min: 16 x1 + 10 x2 + 8 x3 + 9 x4 + 48 xn + 60 xc + 53 xm;

weight: x1 + x2 + x3 + x4 + xn + xc + xm = 1000;
carbon_lower: 0.008 x1 + 0.007 x2 + 0.0085 x3 + 0.004 x4 >= 6.5;
carbon_upper: 0.008 x1 + 0.007 x2 + 0.0085 x3 + 0.004 x4 <= 7.5;
nickel_lower: 0.180 x1 + 0.032 x2 + 1.0 xn >= 30;
nickel_upper: 0.180 x1 + 0.032 x2 + 1.0 xn <= 35;
chromium_lower: 0.120 x1 + 0.011 x2 + 1.0 xc >= 10;
chromium_upper: 0.120 x1 + 0.011 x2 + 1.0 xc <= 12;
molyb_lower: 0.001 x2 + 1.0 xm >= 11;
molyb_upper: 0.001 x2 + 1.0 xm <= 13;
available_x1: x1 <= 75;
available_x2: x2 <= 250;

//	¥H¤U 7 ¥y¥i¬Ù²¤
//	0 <= x1 < +inf;
//	0 <= x2 < +inf;
//	0 <= x3 < +inf;
//	0 <= x4 < +inf;
//	0 <= xn < +inf;
//	0 <= xc < +inf;
//	0 <= xm < +inf;