How many paying stones, each measuring 2 1/2 m * 2 m are required to pave a rectangular court yard 20 m long and 16 1/2 m board?  Choose one:
A) 66  B) 18  C) 16  D) 10  E) 15

Rationale: "20 * 33 / 2 = 5 / 2 * 2 * x = > x = 66 answer : a"
Answer: A