/* ULS problem: LP version - no fixed costs*/ min: 3 x1 + 4 x2 + 3 x3 + s1 + s2 + s3 ; x1 - s1 = 6; x2 + s1 - s2 = 7; x3 + s2 - s3 = 4; /* lp_solve default is non-negative variables */