If there are two companies making the same model of cellphones. Assuming the demand for the cellphones produced by Company 1 is D1, and the demand for the cellphones produced by Compnay 2 is D2, are described by the following two functions: D1=220-P1-(P1-P) D2=180-P2-(P2-P) where P is the average price over the prices of the two companies, i.e., P=(P1 P2)/2. Each company has the cost of C1=C2=10 for producing one cellphone. Suppose each company can only choose one of the three prices {50, 70, 80} for sale