A boat rental company has two kinds of boats, rowboats and motorboats. The expressions below represent the cost, in dollars, for renting each kind of boat for x number of hours.
Cost of a rowboat rental: 8.5x+3
Cost of motorboat rental: 17.50x+25
Which expression shows how many more dollars it costs to rent a motorboat than a rowboat for x hours?
A. 8x+22
B. 9x+22
C. 9x+28
D. 26x+28