I need help please explanation in a short cut way, please.

Mango Systems believes that demand for its pet e-mouse follows a linear demand equation: Quantity =38,480754 Price Mango's variable cost to produce one pet e-mouse is $23.50. Find the maximum total contribution margin (margin per unit times quantity sold) that Mango Systems can possibly achieve on its pet e-mouse. (Rounding: penny.) Answer: 20,761(142,910.85) Question 4 Best Buy sells its pet e-mouse at a price of $40. At that price, it sells 20,000 units, and Price Elasticity of Demand is 3.8. If Best Buy reduces its price by 5.0%, how much will Quantity change, in UNITS sold? (If the change is negative, be sure to use a negative sign.) Answer: (3,800) Question 5 Quik Trip has been selling its pet e-mouse for $52 each. Quik Trip's variable cost is $30 per unit. At that price Quik Trip has been selling 28,487 units per year. Quik Trip is thinking about reducing its price by $4.27 per unit. At the same time, Quik Trip expects to be able to reduce variable cost by $1.76 per unit. By how many UNITS must Quantity demanded change for Quik Trip to just break even on these changes in price and variable cost? (Rounding: tenth of a unit. Use a negative sign if your answer is negative.) Answer: (3,668.7)