Homer Samson has just invented a new cheese grater. He has been travelling around the country exploring marketing opportunities, and discovers that Martin Flores has for the past three years been selling the grater which he developed, using the same process, at his fine food store in Halifax. Homer hopes that by patenting his grater, he can stop Martin from selling his. Martin sees the danger, and decides to also apply for a patent. Which of the following statements is TRUE?

Homer cannot obtain a patent; Martin can.

Homer cannot obtain a patent because his invention was already known and used by Martin.

Whoever registers his patent first will obtain the exclusive right to use it$.$

Martin cannot obtain a patent because his invention has already been on sale for the past three years.