Write a piecewise-defined function to model the monthly cost Cx) (in S) as a function of the number of minutes used x for the month. A 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: C(x)- 55.3, forx s 500 a. 0.35x, C(C) 55.3, C(x)-55.3, C(x)- 55.3, for x > 500 forx s 500 55.3+0.35x, for500 for x s 500 0.35(x 500), for x > 500 b. C. for x s 500 5.3 +0.35(-500), forx > 500