$539 - $35 = $504
$504 : 12 = $42
Per month you pay $42.
To make a positive profit p(x)>0 we need to make:

Now we solve this for x:

We have:
a = -2
b = 7
c = -3
We will use formula for quadratic equation:

We got two solutions. One is fraction other is whole number. We will not consider fraction because the amount of muffins sold must be whole number. So our solution is:
x>3
4136/8= 517
The others
7116/8=889.5
4309/8=538.625
9406/8=1175.75
The only system that has infinitely many solutions is NUMBER 2. Where you solve a system, and both sides end up being 0=0, then the system will have infinitely many solutions. Well, in these four choices, Number 2 is the only one that ends up being 0=0 after I solved it.