The total age of A and B is 12 years more than the total age of B and C. C is how many year younger than A?	Select the correct option.
A) 10
B) 11
C) 12
D) 13
E) 15

Rationale: "given that , a + b = 12 + b + c ⇒ a - c = 12 therefore , c is younger than a by 12 years answer is c ."
Answer: C