12 patterns:
[50]*2 = 100
[50]+[40] = 90
[50]+[30]+[20] = 100
[50]+[20]*2 = 90
[40]*2+[20] = 100
[40]+[30]*2 = 100
[40]+[30]+[20] = 90
[40]+[20]*3 = 100
[30]*3 = 90
[30]*2+[20]*2 = 100
[30]+[20]*3 = 90
[20]*5 = 100

Optimal solution - 82:
([50] + [50]) * 10
([30] + [30] + [40]) * 40
([20] + [20] + [30] + [30]) * 20
([20] + [20] + [20] + [20] + [20]) * 12

10 + 40 + 20 + 12 = 82

how to add minimum demand?