Write a program that translates a letter grade into a number grade. Letter grades are A, B, C, D, F, possibly followed by + or -. Their corresponding numeric values are 4, 3, 2, 1, and 0. There is no F+ or F-. A + increases the numeric value by 0.3; a - decreases it by 0.3. However, an A+ has the value 4.0