If a-b= 9 and a^2+b^2=281, find the value of ab Choose the correct option.
A) 100 B) 12 C) 15 D) 18 E) 19

Rationale: "2 ab = ( a ^ 2 + b ^ 2 ) - ( a - b ) ^ 2 = 281 - 81 = 200 = > ab = 100 answer : a"
Answer: A