lingo出现错误提示，求教

max=y;y <= (2*x1+5*x2+7*x3+x4-20)/68;y <= (4*x1+x2+3*x3+11*x4-33.33)/266.67;y <= (9*x1+3*x2+x3+2*x4-40)/410;y <= (75-1.5*x1-2*x2-0.3*x3-3*x4)/45;y <= (70-0.5*x1-x2-0.7*x3-2*x4)/45;3*x1+4.5*x2+1.5*x3+7.5*x4 =150;