Alex makes ceramic bowls to sell at a monthly craft fair in a nearby city. Every month, she spends $50 on materials for the bowls from a local art store. At the fair, she sells each completed bowl for a total of $25 including tax. Which equation expresses Alex's profit as a function of the number of bowls that she sells in one month.

1) p(x) = 50x+25
2) p(x) = 15x+25
3) p(x) = 25x
4) p(x) = 25x-50

Why?