The task is to generate the correct answer for a given math problem.

[EX Q]: Problem: how many digits are required to number a book containing 240 pages ?
[EX A]: 612

[EX Q]: Problem: find the area of trapezium whose parallel sides are 20 cm and 18 cm long , and the distance between them is 20 cm ?
[EX A]: 380 cm 2

[EX Q]: Problem: the avg weight of a , b & c is 84 kg . if d joins the group , the avg weight of the group becomes 80 kg . if another man e who weights is 8 kg more than d replaces a , then the avgof b , c , d & e becomes 79 kg . what is the weight of a ?
[EX A]:
80