Find the average of all the numbers between 6 and 34 which are divisible by 5.  Select the correct option:
A) 18 B) 20 C) 24 D) 30 E) 32

Rationale: "solution average = ( 10 + 15 + 20 + 25 + 30 / 5 ) = 100 / 5 = 20 . answer b"
Answer: B