The discount is given on the basis of  the plan whatever they mention for eg50+20% means not 70%it means first 50% discount of the main cost and after that 20 % of that cost which meet after the 50 % discount
answered question
Advertisement is the good way to tell about the product to the public through the advertisement 30% business increase for the particular product eg movies adds before the movie  release get the money to the producer  as the spend to make the movie whether it is flop but the advertisement  get the customers