The senior class advisor at a local high school is printing class tee-shirts as a fundraiser. The printing company charges three dollars per shirt if fewer than 100 tee-shirts are ordered, plus a flat 25 dollars order charge. If 100 or more tee-shirts are ordered, a fee of two dollars and fifty cents is charged per shirt, and the order charge is reduced to 15 dollars. Write the piecewise function C(x) to represent the printing fees.