Objective If there are several solutions find that one which uses the minimal
number of assigned values.
If there is no solution minimize the cost function with the following
coefficients:


             a1 =  4
             a2 =  3
             a3 =  2
             a4 =  1
             b1 =  0
             b2 =  0
             b3 =  0
             b4 =  0