A certain rental car company charges a flat fee of $30 plus an additional 25 cents per mile when the number of miles driven is less than or equal to 100 miles. For any miles driven over 100, the company reduces the price per mile to 20 cents. Write a piece-wise function that describes the charges, C(x), to a customer who drives x miles. Use the function to predict the charges when driving 50 miles and when driving 150 miles.