In c++, write a program (only using header file #include ) that translates a letter grade into a number grade. Letter grades are A, B, C, D, and F, possibly folled by + or -. Their numberic values are 4, 3, 2, 1, and 0. There is no F+ or F-. A + increases the numeric value by .3 while a - decreases it by .3. An A+ has a value of 4.0.