ex [1, 2, 4, 5, 7, 9]
e_i [2, 4, 6, 7, 9, 10, 11]
slack ['0', '2/3', '1/3', '1', '2/3', '1/3'] 11-8a+c = 0 2a-c = 1
min e_i/i, i<=7: 11/7  i<=6: 5/3
