Please help with the following problem.
Natsano has at most $50,000 to invest in common stocks of two companies. He estimates that an investment in company A will yield a return of 10%, whereas an investment in company B, which he feels is a riskier investment, will yield a return of 20%. If he decides that his investment in the stock of company A is to exceed his investment in the stock in company B by at least $20,000, determine how much he should invest in the stock of each company in order to maximize the return on his investment.