Add function on wordpress website

We made wordpress website for car rental agency with that theme: [login to view URL] All We need is to add a car discount function on website. 1. Look at [login to view URL] - It should be on "add product" page. And administrator should be able to make discounts by percentage on any cars. Also admin should be able to choose a discount Schedule 2. look at [login to view URL] - When an user sets up pickup and dropoff dates, the new price should be calculated automatically on "Car listing" and "Single car" pages. for better experience look at [login to view URL] and [login to view URL] THATS ALL ABOUT DISCOUNT.