2.1.6 Sympy

A grade: { 1, 2, 3, 4, 6, 8, 9, 10, 11, 16, 17, 18 }

B grade: { 5, 7, 12, 13, 14, 15, 19, 20, 21 }

C grade: { }

F grade: { 22, 23, 24, 25, 26, 27, 28, 29, 30 }