A? student's course grade is based on one midterm that counts as 20?% of his final? grade, a class project that counts as 15?% of his final? grade, a set of homework assignments that counts as 50?% of his final? grade, and a final exam that counts as 15?% of his final grade. His midterm score is 72?, his project score is 93?, his homework score is 78?, and his final exam score is 69. What is his overall final? score? What letter grade did he earn? (A, B,? C, D, or? F)? Assume that a mean of 90 or above is an? A, a mean of at least 80 but less than 90 is a? B, and so on.