A rectangular garden that is 10 feet long and 5 feet wide is to be

A rectangular garden that is 10 feet long and 5 feet wide is to be covered with a layer of mulch 0.5 foot deep. At which store, K or L, will the cost of the necessary amount of mulch be less?

Total volume of mulch requires is 10*5*0.5 = 25
(1) Store K sells mulch only in bags, each of which costs $7 and contains 6.25 cubic feet of mulch --> no info. about L....insufficient
(2) Store L sells mulch only in bags, each of which costs $40 and contains 25 cubic feet of mulch --> no info. about K...insufficient

1+2 -->from 1: we need 25/6.25 = 4 bags, cost of 4 bags is 4*7 = $28
from 2: we need 1 bag, cost of 1 bag is $40
hence K is cheaper.....sufficient

Ans. C)