An online shopping company has t-shirts for sale. The sales tax rate is 7.25% on each shirt ordered, and there is a flat fee of $4.75 shipping for the entire order. There is no limit on the number of t-shirts one person can purchase. Considering an expression that models the total cost on any online purchase, what is the value of the constant term and what does it represent?

A
0.725 represents the sales tax

B
7.25 represents the sales tax

C
4.75 represents the shipping charge

D
7.25 represents the shipping charge