Hannah buys red shirts, blue shirts, and yellow shirts at a cost of $28.75 each. Which expression represents the total cost, C, of the shirts, if r represents the number of red shirts , b represents the number of blue shirts, and y represents the number of yellow shirts? Plz show work and explain your work :)

A. C= 28.75 ( r + b+ y )
B. C= 28.75 ( r - b - y)
C. C= 28.75 + r + b + y
D. C= 28.75 r + b+ y