Find the average of all the numbers between 40 and 80 which are divisible by 3.  Choose one
A) 15	B) 70	C) 20	D) 60	E) none

Rationale: "sol . average = ( 42 + 45 + 48 + 51 + 54 + 57 + 60 + 63 + 66 + 69 + 72 + 75 + 78 / 13 ) = 780 / 5 = 60 . answer d"
Answer: D