2. Total price of 10 items sold =10x12 =120 yuan; Cost price c = 81+3x10 =11; So the profit from selling 10 items =120-11= 9 yuan.
3. If the price of goods is 2 yuan, it is impossible to calculate the cost C=8 1+3Q=2Q and deduce that q is negative. So the commodity price should not be 2 yuan/piece.