A student's course grade is based on one midterm that counts as 15% of his final grade, one class project that counts as 25% of his final grade, a set of homework assignments that counts as 40% of his final grade, and a final exam that counts as 20% of his final grade. His midterm score is 62, his project score is 98, his homework score is 91, and his final exam score is 74. 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. Whats his final score ?