Write a piecewise-defined function to model the monthly cost C(x) (in $) as a function of the number of minutes used x for the month. cell phone plan charges $45.75 per month, plus $9.55 in taxes, plus $0.35 per minute for calls beyond the 500-min monthly limit. Select one: O a. C(x) = 155.3, for x 500 X Ob. C(x) = {55.3, for x 500 O c. C(x) = 155.3, for x 500 O d. C(x) = 155.3, for x 500