A store purchase 20 coats that each cost an equal amount and then sold each of the 20 coats at an equal price. What was the store's gross profit on the 20 coats? 1) If the selling price per coat had been twice as much, the sotre's gross profit on the 20 coats could have been $2400. 2) If the selling price per coat had been $2 more, the store's gross profit on the 20 coats could have been $440. 为什么答案是b呢？ | 
