creates example data set

def make_data():
    """creates example data set"""
    I,d = multidict({1:80, 2:270, 3:250, 4:160, 5:180})            # demand
    J,M,f = multidict({1:[500,1000], 2:[500,1000], 3:[500,1000]}) # capacity, fixed costs
    c = {(1,1):4,  (1,2):6,  (1,3):9,    # transportation costs
         (2,1):5,  (2,2):4,  (2,3):7,
         (3,1):6,  (3,2):3,  (3,3):4,
         (4,1):8,  (4,2):5,  (4,3):3,
         (5,1):10, (5,2):8,  (5,3):4,
         }
    return I,J,d,M,f,c