We know that the total of seats for this case are 61000 so we have the following equation:

We also know that the number of seats in Secton A equals the total number of seats in sections B and C so then A=B+C

Then the value of A =30500
Now we can create a function for the cost and we got:

Replacing the value of A we got:

And rewriting the first equation we got:

Solving for B we got: B=30500-C and replacing in the before equation we got:

And solving for C we got:

