If a-b= 4 and a^2+b^2=80, find the value of ab
Choose the correct option
A) 10 B) 12 C) 15 D) 18 E) 32

Rationale: "2 ab = ( a ^ 2 + b ^ 2 ) - ( a - b ) ^ 2 = 80 - 16 = 64 = > ab = 32 answer : e"
Answer: E