A local publication charges by the character for its classified ads. Letters, numbers, spaces, and punctuation each count as one character. They charge $46 for the first 200 characters and $0.15 for each additional character. 

a. If x represents the number of characters in the ad, express the cost c(x) of an ad as a piecewise function.
b. Graph the function from part a.
c. Find the coordinates of the cusp in the graph in part b.