Linear Programming-Investment Strategy

Question

Invest at most $90,000 in securities in the form of corporate stocks. Options into three groups of stocks: blue-chip stocks will yield 3% return (dividends and capital appreciation) within a year, growth stocks will yield 10% return within a year, and speculative stocks will yield 16% return (mainly due to capital appreciation) within a year. Because of the relative risks involved in his investments, he has further decided that no more than 25% of his investment should be in growth and speculative stocks combined, and at least $18,000 of his investments should be in growth stocks. Obviously he wants to maximize his return on investment (ROI) and he wants his ROI to be at least $4,400 in the year.

I am completely lost and cannot figure out how to set this up. Can someone please help?