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. 

<code>
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
</code>