5. (10 points) When the price of a glass of lemonade at a lemonade stand was $1.75, 400 glasses were sold. When the price was lowered to $1.50, 500 glasses were sold. Assume that the demand function is linear and that the marginal and fixed costs are $0.10 and $25, respectively. number of lemonade, price P) a. Find the demand equation p = mx + b