题目

阅读下面的短文，然后按照要求写一篇150词左右的英语短文。    Some years ago, leaving the farm to work in the city, three brothers were employed by the same company and on the same pay. But three years later, they received different wages. So their father was confused and decided to pay a visit to the boss, who told him that he would let his sons explain for themselves.                          The three brothers were asked by the supervisor to go to the airport to get a cargo inventory at different times. Jim, who received 500 dollars a month,在四棱锥P-ABCD中，侧面PCD⊥底面ABCD，PD⊥CD，E为PC上一点，且PE=12EC，F为AB上一点，且AF=2FB，底面ABCD是直角梯形，AB∥CD，∠ADC=90°，AB=AD=PD=1，CD=2．（Ⅰ）求证：EF∥平面PAD；（Ⅱ）若Q为侧棱PC中点，求二面角Q-BD-C的正切值．