Waluigi's Towing Service charges $38.51 for its hook-up fee plus $35.21 for every mile, m, they tow your car. The equation that models the total cost (T) is T(m) = 35.21m + 38.51. Which value in the equation represents the rate of change?

A .. The number of miles towed
B .. $38.51
C .. $35.21
D .. $73.72