this is my exam. I think you can find good idea.
variables
x1,x2,y1,y2,func,w1;
positive variables
x1,x2,y1,y2;
parameters
x1L,x2L,y1L,y2L
x1U,x2U,y1U,y2U;
x1L=0;
x2L=0;
y1L=0;
y2L=0;
x1U=0;
x2U=0;
y1U=0;
y2U=0;
equations
eq,eq2,q1,q2,q3,q4,q5,q6,we1,we2,we3,we4;
eq.. func=e=x1-x2-y1+x1*y2;
eq2.. func=e=x1-x2-y1+w1;
q1.. x1+4*x2=l=8;
q2.. 4*x1+x2=l=12;
q3.. 3*x1+4*x2=l=12;
q4.. 2*y1+y2=l=8;
q5.. y1+2*y2=l=8;
q6.. y1+y2=l=5;
we1.. x1L*y2+y2L*x1-x1L*y2L-w1=l=0;
we2.. x1U*y2+y2U*x1-x1U*y2U-w1=l=0;
we3.. -x1U*y2-y2L*x1+x1U*y2L+w1=l=0;
we4.. -x1L*y2-y2U*x1+x1L*y2U+w1=l=0;
*x1.lo=0;
*x2.lo=0;
*y1.lo=0;
*y2.lo=0;
*x1.up=10;
*x2.up=10;
*y1.up=10;
*y2.up=10;
model mccormick/eq2,q1,q2,q3,q4,q5,q6,we1,we2,we3,we4 /;
option lp=cplex;
solve mccormick minimizing func using lp;