Discount Single - Brands

Creating LOCK on the site, for any product has a discount rate of 5% instead of the discount by way of payment. Change the value of the discount only.
If the cart is placed more than one product, and some of them are not brand discount differential prevails largest discount that is the method of payment.
Creation of administrative which will list all the brands and for each of the option of placing value 1.
At the time of the trolley, it is the largest discount (pmt form or brand)