student's course grade is based on one midterm that counts as 10% of his final grade, one class project that counts as 25% of his final grade, a set of homework assignments that counts as 35% of his final grade, and a final exam that counts as 30% of his final grade. His midterm score is 64, his project score is 90, his homework score is 91, and his final exam score is 64. 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.