Even Quik Trip has a pet e-mouse. Quik Trip has been selling its pet e-mouse for $49 each. Quik Trip's variable cost per unit is $25. Quik Trip is thinking about raising its price by $5 per unit. By what percent must Quantity demanded change so that Quik Trip will have the same total contribution before and after the change in price? (Rounding: tenth of a percent. Report 36.5%, for example, as "35.6". Use a negative sign if your answer is negative.)

ANS: -17.2