求1+2+2²+2³+…+2²⁰¹⁶的值，可设S=1+2+2²+2³+…+2²⁰¹⁶，于是2S=2+2²+2³+…+2²⁰¹⁷，因此2S﹣S=2²⁰¹⁷﹣1，所以S=2²⁰¹⁷﹣1．我们把这种求和方法叫错位相减法．仿照上述的思路方法，计算出1+5+5²+5³+…+5²⁰¹⁶的值为（   ）

    Two farmers were on their way home one evening after a hard day's work．Both were tired．They happened to look up at the sky and saw a black cloud overhead．
    "Ah!" said one farmer, "tomorrow we shall have rain and the rice will grow well．" The second answered, "Nonsense （胡说）, the rain will only kill the crops （庄稼）．"
    So they began to fight．Just then a third farmer came along and asked them why they were quarreling（争吵）．Both farmers explained about the black cloud．
    "What cloud?" asked the third farmer．They all looked at the sky．The cloud was no longer there．

中国气象局国家空间天气监测预警中心的监测数据表明，进入2012年7月份以来，多项标志太阳活动水平的参数保持高位。回答下列问题。