min:      15 A + 7 B + 9 C +10 D;
                                 
material:  3 A + 6 B + 5 C + 4 D <= 4000;
labor:     2 A + 5 B + 4 C + 3 D <= 3300;
contract:                C       >=  400;
delivery:    A +   B +   C +   D  = 1000;

//	¥H¤U¥|¥y¥i¬Ù²¤
//	0 <= A < +inf;
//	0 <= B < +inf;
//	0 <= C < +inf;
//	0 <= D < +inf;