The overall grade in the end depends on your actual score, not the letter grade of the midterms. There are no A+ / A- etc assigned for midterms.
100 A 100 A 98 A 98 A 98 A 96 A 95 A 95 A 93 A 92 A 92 A 92 A 91 A 83 B 81 B 80 B 79 B 79 B 78 B 78 B 77 B 76 B 72 B 70 B 69 B 68 B 67 B 61 C 58 C 57 C 57 C 56 C 56 C 54 C 53 C 53 C 52 C 52 C 49 C 49 C 47 C 45 C 43 D 42 D 41 D 40 D 39 D 38 D 37 D 37 D 35 D 34 D 33 D 33 D 32 D 31 D 31 D 29 D 26 D 21 D 17 D