What is the range of function for this situation?

Question

A set of weights include a 4lb barbell and 6 pairs of weight plates.  Each pair of plates weighs 20lb.  If x pairs of plates are added to the barbells, the total weight of the barbell and plates in pounds can be represented by f(x) = 20x + 4.Range 

Answer 1

R = {4, 24, 44, 64, 84, 104, 124}