The equation for the first option would be

Where "x" is the number of copies and y the cost.
The second equation will be

If we graph both equations we have
As we can see, they will be equal in terms of cost with 2 copies. The cost will be 50.
We can see it at the intersection of the two graphs! we can also do it with algebra, if the costs are equal (same "y") we can say

The number of copies is 2.