You are a mango vendor at the supermarket in the City of Naga and the mango is sold for Php 90.00 per kilogram (k). You promise to give a Php20.00 discount if the customer will buy at least 3 kilograms. What is the function that represents the cost of mango per kilogram (k). (Note: the vendor can sell in %, %, and %) s. You wish to celebrate your birthday with your friends at Yakimix in SM Seaside, an eat all you can restaurant that costs Php599.00 per head. The restaurant gives a birthday promo that one additional person will be free if there are at least three paying customers Represent the amount you need to pay as a function of the number of friends (f) you invited.​