A:★÷(1+ 19 )
B:★ × (1+ 19 )
C:★ × (1- 19 )
D:★÷(1- 19 )
已知x,y满足约束条件x-y≤0x+y-1≥0x-2y+2≥0若的最小值为4,则z=x+3y+m,则m=( )