If a = (3)b and c = 5b, then which of the following represents the average (arithmetic mean) of a, b, and c, in terms of b ?  Choose the correct choice from the following answers
A) b/3
B) b/4
C) 2b
D) 3b
E) 5b
a = (3)b and c =5b.   The mean = (a + b + c)/3 = (3b + b + 5b)/3 = 3b.   Answer is 3b
<result>D</result>
If a = (3)b and c = 5b, then which of the following represents the average (arithmetic mean) of a, b, and c, in terms of b ?