creates example data set

def example():
    """creates example data set"""
    J,v = multidict({1:16, 2:19, 3:23, 4:28})
    a = {(1,1):2,    (1,2):3,    (1,3):4,    (1,4):5,
         (2,1):3000, (2,2):3500, (2,3):5100, (2,4):7200,
         }
    I,b = multidict({1:7, 2:10000})
    return I,J,v,a,b