If a(a - 4) = 21 and b(b - 4) = 21, where a ≠ b, then a + b =	Choose the correct choice from the following:
A) − 48 B) − 2 C) 4 D) 46 E) 48

Rationale: "a ( a - 4 ) = 21 and b ( b - 4 ) = 21 = > a , b must be integers and if a is - 3 or 7 , b will be 7 and - 3 respectively = > a + b = 4 ans : c"
Answer: C