Using min/max *within* an Integer Linear Program
Add in an auxiliary variable, say x4, with constraints: x4 >= c1*x1 x4 >= c2*x2 x4 >= c3*x3 Objective += c4*x4
Add in an auxiliary variable, say x4, with constraints: x4 >= c1*x1 x4 >= c2*x2 x4 >= c3*x3 Objective += c4*x4