Using Walkers crisps as an example describe the role of promotion within the marketing mix?

Using Walkers crisps as an example describe the role of promotion within the marketing mix?
The 4 p's of marketing mix are price, product, place and promotion.Product: Walkers crisps or any product that they sell. Does it have a unique selling point?Place: huge supermarkets e.g. ASDA, TESCO, Sainsbury, vending machines, to wholesalers and retailersPrice: multipacks of crisps. psychological prising e.g. 1.25, 0.90Promotion: TV adverts, billboards, paid ads,-special offers, selling crisps cheaper than other companies.