A student's course grade is based on one midterm that counts as 15% of his final grade, one class project that counts as 5% of his final grade, a set of homework assignments that counts as 45% of his final grade, and a final exam that counts as 35% of his final grade. His midterm score is 66, his project score is 94, his homework score is 84, and his final exam score is 61. 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. His overall final score is (Type an integer or a decimal. Do not round.) His letter grade is