The science club is comparing options for purchasing new T-shirts. One company charges a $100 base fee plus an additional $3.50 per shirt. A second company charges a $120 base fee but only an additional $2.50 per shirt. The given expression representsthe difference of the two companies’ average cost per shirt.
(3.5x+100)/x - (2.5x+120)/x
Which expression is equivalent to the expression representing this situation?

a. x-120
b. (x+220)/x
c. 6x+220
d. (x+220)/x