10. Model with Mathematics A con prepaid mobile phones. It purchases them for $12 each and uses a markup rate of 250%. A What is the markup rate in decimal form? 10% 48 COUN B. The markup rate is the constant of proportionality in the equation y = kx. Write an equation that can be used tos find the markup on the cost x of a phone. OX c. Using the equation, calculate the markup amount. D. What is the retail price of a phone? Next week the store is going to reduce the price to $31.50. E. Calculate what percent the sale price is of the retail price. Show your work.