Sometimes go to the supermarket or convenience store, there will always see some groups of goods are sold,called set sales. For example, one had five cents a ham, but the business took ten ham bundled with the sale, is five dollars, fifty cents to waste a lot of people are not prepared, the supermarket you have to find coins , is very convenient. There are 5 dollars a pound of rice, soybeans 10 dollars a pound, most people want to buy rice, buy beans, then put a pound of rice and a pound business soybeans sold in a box together, this is a step up sales the plan.