The mower

Well, with appreciated help from my Brother-in-law, we took a look at the mower my older sister fouled up. He noticed some black stuff flowing out of the gas tank as he dumped it out and then did his best to clean it out further with a rag. In spite of the best efforts, it was decided the spark plug is fouled because of the water and dirt that was dumped in out of the red plastic gas container. So I need a plug for a 3.5 HP Briggs and Stratton engine. I think my older sister should have to pay for it if she doesn't buy a new mower, which is probably what we need. I want a new electric motor for the electric lawn mower we have now if anything.