第四十章控制变量（2 / 2）

PmMvPA2NgOOCgOO6uuSEmueRiOaoiuW6uuSJnOairOacluWNuOSfueSRiOaMgOM+Yzw+Yy88DZq874O45aOu5bml5bmv5aic5a+Y5o+D5YiP5Yy876yQ5ZSw5rqp55m757Sv6K+Y5o+D5Yy874695IGe5pe+5YuO5ZSw5q2v6Iy876OP5YC85bCj5Y695Ja75Iy877SX6aye54Sa54q45LOF5au/5aiX6T5jPD5jLzwNgoDjnL/osLXouaXlgJ3ni5znjLzvsJzln47lqJzlmavnr5jmqo/lPmM8PmMvPA2CgOO9v+ihsuaPmeaAmOaMh+U+Yzw+Yy88DYKA44C85bum56u66Ky96Lu96Lu96Iq85D5jPD5jLzwNjYDjgoDjgLHlhJrnvaXlvq7okYjmqIrlurrkiZzmoqzmnJbljbjkkYjmlIDilIDioL3kkobpkI/mobLmkYjmqoDmq4jln7nkoL3ko4LpjIDjPmM8PmMvPA2NgOOCgOOTgemln+eRiOaMgOM+Yzw+Yy88DY2A44KA44i55IC75LK55aic5aC95JOB6aWf572l5YCc5qC95IyA4z5jPD5jLzwNgoDjoZXllpLlhJrniY7mt4blsbDlqZfmr53mo4Lph7/opY7mtKTljr3kqo/ljLzvvJzngLjklrvki5znjYblobLmjLzvgLzlo4zmr5jmmL/oiLvngJzmuaXlPmM8PmMvPA2CgOOAvOW+neahsuaWu+SGveQ+Yzw+Yy88DYKA45q85Lqc5oSa54uJ5raU5qGs5oC45Ja75Jm756ic5a+Y5o+D5Yy877yc54C45Ja75Ia65Kqe54Sa57y85IqR5aat6Iy875Kn56CH5Ya65Ji76Ymy5rml5T5jPD5jLzwNgoDjp4DmpZXntb7khJrnrKHnurzlgJ3nprjlk4Hpm4rlhr3kjLzvjYfpjbjknL3kqIrlPmM8PmMvPA2CgOOVheiLieaGuuSPveSvieaLiea4vOSWu+Sroui0jeWMvO+wteiBpuiruuisveg+Yzw+Yy88DY2A44KA44mc5qGy5r2D6byg5oS16ISa54yH6Zm/6Kic5ZmV556/6Kmk5aqT5aC95IO/5Y+w5YyA4z5jPD5jLzwNgoDju6bnnbfogLzliYvmlrvkn7fojLzvpa3mgLjkhrrkgIDpjpDlgL7luaXlPmM8PmMvPA2NgOOCgOONveS6qeeEmueRiOaZu+evguiNuOSgveSoiuWonOWUgOKUgOKvmOaRiOaMgOM+Yzw+Yy88DY2A44y877q65ISa56C95KiK5a+Y5o245JGI5oyA4z5jPD5jLzwNgoDjs5/psKPlhJrnurrkqrjkgLjklrvkqYnlqo/ljLzvk4HpmoDphJrnjJXnlqTljrjkuaXlu63mgbDlgaboj4Pll77ljr3kv7rnsKPljLzvp77ks4DouaXlkb/ooJ3pjLzvtKTljr3kjLzvpa3mgLjkjYnlgL7lj5nmgJjmjIflPmM8PmMvPA2CgOOMlee5vuiEmueNv+W5ruW9g+i6h+WSiOWwluaNh+monOWPg+WMvO+dr+iEmue5peU+Yzw+Yy88DY2A44KA47iu6IGF5ZGI5p6d6aSZ6YyA4z5jPD5jLzwNjYDjgoDjurrklb3ku7vkhJrnko7mia7lkYjmqIrlq4jlhr3kjIDjPmM8PmMvPA2NgOOCgOOlu+Svj+WRiOauuOWBpuiMgOM+Yzw+Yy88DZq875y+5qCX5qKz5qCX5oy875md6beG5ZSw5q2v6Iy875Kn56CH5Ya65Ji76Ymy5ru96Lu96Iq85D5jPD5jLzwNjYDjgoDjr5jmjLzvi7rktrvkmb/oqaTlirvkkbDls4fojIDjPmM8PmMvPA2NgOOfvO+9peW0m+aXvuWGkOeEpOWgveSXvuWJp+igveSMgOM+Yzw+Yy88DYKA44mc5rG35bq45K6N5oek5YaH5Yy875a75IyA6Iy877iu6Ji76Ya65Jm754+757K35bml5T5jPD5jLzwNlIDilIDir5jmjIDojLzvjYDjjrjkgo/lvYPoppDlr5jmjIDjr5jmjbjkPmM8PmMvPA2CgOOln+eKkeWonOWWu+Q+Yzw+Yy88DYKA46Wd5ou45Ia65LeG5ZO855O8556l57yc56+Y5qqP5Yy8752v6LSv6LuI5Yur54mc5qGy5rml5T5jPD5jLzwNjYDjgoDjt6Dmmb/orbvnp7vnoL3ks4PmjbjkkYjmhr3kjIDjPmM8PmMvPA2NgOOCgOOTgemln+eRiOaMvO+GkOeEpOWqh+iyuuSavOSgveSMvO+LuuS6h+W6uuSbuuSjgumCgOOzhuWjp+ixt+Wqh+i0m+eAuOSgveSzg+aNuOSRiOaMgOM+Yzw+Yy88DYKA45WA5q+P5Ze+5Zmd6bSN5Z6l57yc54y877u96Ii+5ZSw5q2v6Iy877ml5YCd54uc55a75D5jPD5jLzwNjYDjgoDjoL3kjIDjPmM8PmMvPA2CgOONk+WhjeWwo+WjgumBp+iskOWNieaonOWwjue5peWMgOiMvO+BlOmGuuS9kOiyt+Wpl+aIueSAu+SJnOavmOY+Yzw+Yy88DZSA4pSA4o+E5rOG5YSa55GK5ouO5bSH6IGe5o2n54C45Imc5qqP5Yy876q754WD5pa75LaF5Ymc5qGy5oyH6ZCt5bic57KJ6LCB54Sa55a75D5jPD5jLzwNjYDjn7zviLnkgLvkirjkkbvnoL3kjIDjPmM8PmMvPA2CgOOPh+mNh+mEmueMh+mdr+iWu+SFuOaskOWjreafnOehrOaAuOSsrOeMvO+dh+WAuOSJheW4nOe5peU+Yzw+Yy88DY2A44KA44a65LuO5Yq45JG754+757K35ZGI5rq45KCb5YyA4z5jPD5jLzwNmrzvqZnpsY3lvYPpqrvnhYPmlb3ku7vklK/mtI3ljLzvj7zkt7XoobLmjrnkoIfls5/psKPljLzvkqfngLjkhrrknIHllrvkPmM8PmMvPA2NgOOCgOOMh+mZv+ionOWZleelr+iNuOSRiOaUgOKUgOKRiOaJr+iKkeWjj+WyuuSonOWwjuegveSenemkmemMgOM+Yzw+Yy88DY2A44KA44Sa55qB5aWv6JGI5pqB5a2756e755q85JGI5oa95IyA4z5jPD5jLzwNjYDjjLzvna/otK/ojbjkrbvnp7vnpbvkr4/loL3kjIDjPmM8PmMvPA2CgOObv+iojuanvuSFhuWEmue/uueymOm5peWAvuWCseWCseWAuOSMvO+DsOitr+iEmueZnem3huWbv+i5o+iFjOWyrOaJnOagjeWJnOaAieaGsOWMvO+OveSKtuiLjuWKtuizn+mwo+WWu+Q+Yzw+Yy88DY2A44KA44uc57m+6IGX5qic5Zmr56qP5Zq85I245LGw5Yy876Wd5ou45JmV55GI5oyA4z5jPD5jLzwNjYDjgoDjhrrkpZ3mm7/okYjmqa7ooL3kurjkoJvlr5jmjLzvi4nmko/mkYjmjIDjPmM8PmMvPA2CgOO/uueVuuWEmue5peWziOaonOWvmOaPg+WfueSMvO+ijuaVr+ionOWvmOaPg+WMvO+QvuWNuOS+lueNuOSDsOitr+iWu+Q+Yzw+Yy88DY2A45+877uH5a+P5YiH5qCX5oGA44aH5b6y54y877eg5oC45ICI5a+c5ouJ5oSa56C95J+36I+A46eO5oyO5o6A44Sa56C95I6Y5oGv6IyA4z5jPD5jLzwNjYDjn7zvtojlp47mvYPovYPpiLnkgLvkoL3kjLzvjpjmga/os4Pmr5jmqo/loL3kr5jmmL/ojIDjPmM8PmMvPA2CgOOJsuaAuOSepee8nOeWu+Q+Yzw+Yy88DY2A45+874a65IaQ54mc5pi/6Iy876mZ6Ym25rG35aqH6KC95J+874u65Jqk5ZGI5qqA5pKA5aic5bCO54yA4z5jPD5jLzwNgoDjsJzlhqLphJrnuaXlm7/oqbjoj4PlvYPppa3mgLjkj6/mtI3ljLzvu73ogZ7mpa3mmoTojLzvkb/ooJ3puK/luK/lgLjkjLzvuaXlgJ3nkZDllrvkPmM8PmMvPA2CgOOUsOargee5gueAuOS6h+WAv+asoee0mOWEmue5peWrouiPmeaAmOaMh+U+Yzw+Yy88DY2A45+876C95Ja16J2+5JGI5oy877WR5YyA4z5jPD5jLzwNmrzvu4fljY/lkaznt4bljpDlkqfngLjkqJzltI3ljLzviYXlrpvnnpvltpTmsJzlvYPorJzmuaXljLzviLnkgLvkhrrksIjluojlna/opY/lo4Lpr5jmj4PlPmM8PmMvPA2CgOO/oemAuOSuvuWuvuW4kOW8keW5peU+Yzw+Yy88DY2A44KA47q65ISa55a16J2+5Kic5Y+757K35bSN5Yy876Su6L+J5qKV5o245KC95K+Y5pGI5oyA4z5jPD5jLzwNgoDjlJ/mqbjmjrnkkb/olLDmra/ojLzvuaXlgJ3ni5znn5znpK7ojIDojY/ljLzvv4HpjbjklrvkjYDjgoDjr5jmjbjkjIDjPmM8PmMvPA2NgOOfvO+6uuSkiuaRm+eEmueRiOafvO+IueSAu+SvmOaonOWwjuegveSlu+SAieaMgOM+Yzw+Yy88DZq875ud57yc54Sa55a75ICd56+b57Cc5amI5ZCU6Z6l57yc54y874695IuO5ZSw5q2v6Iy876Wt5oC45I2J5Yq45LC16Lml5T5jPD5jLzwNgoDjrLDoko3osIjln4Tmnq7li7rkhJrngafojbjkjIDohqfotJvngLjkuaXlqrjkkJ/mua/ljLzvu73ojIDot4bljLzvsKPlgLjkkaznu73otoTnvb/luaXlPmM8PmMvPA2CgOOYu+mJsuavmOaqj+U+Yzw+Yy88DYKA45St556b5buI5Yur56Gy5pa75D5jPD5jLzwNjYDjn7zvhJrni6flgLzlmYDltpfmiLnkgLvkjIDjmrzvmZ3pt4blsononqXnjLzvlrvkgJ3ni5znuaXlPmM8PmMvPA2NgOOCgOOtgeeoheWavOSMgOM+Yzw+Yy88DY2A45SA4pSA4ruO5Yu45LC16JWz5pKO5qq45KOC6aC95KeF54y876y75Ja75Imc5qGy5pye5oKm5YyA4z5jPD5jLzwNjYDjgoDjqrjkgY/lo4LphrrksLXooY3mrLvklrvkjLzvvaXlmojljIDjPmM8