pb solving algebra II 10th grade

This is what I have: One of the dolls that Dolls R Us manufactures is Talking Tommy (TT). Another doll without the talking mechanism is called SIlent Sally (SS). In one hour, the company can produce 8 TT or 20 SS. Because of the demand, the Cie knows that it must produce at least twice as many TT as SS dolls. The Cie spends no more that 48 hours per week making these two dolls. The profit on each TT is $3 and on SS is $7.50. How many of each dolls should be produces to maximize profit each week? What is the profit?

I have no idea of how to solve it. It is urgent. Thanks