Mia opens a coffee shop in the first week of January. The function W(x) = 0.002x3 - 0.01x2 models the total number of customers visiting the shop since it opened after x days. She then opens an ice cream parlor in the month of February. The function R(x) = x2 - 4x + 13 models the total number of customers visiting the parlor since it opened after x days.
Which function represents the difference, D(x), in the number of customers visiting the two shops?
D(x) = 0.002x3 + 1.01x2 - 4x + 13
D(x) = 0.002x3 + 0.99x2 + 4x - 13
D(x) = 0.002x3 - 1.01x2 + 4x - 13
D(x) = 0.002x3 - 0.99x2 - 4x + 13