At the point of sale, the merchant would calculate the amount owed by the customer and indicate the amount, and may prepare an invoice for the customer (which may be a cash register printout), and indicate the options for the customer to make payment.
Performing push-ups works a variety of muscles in your upper body, including specific muscles within your abdomen, chest, shoulders and upper arms. You can vary your technique by placing your hands at different widths to emphasize one area over another.
Here is a graphic of the muscles used in push ups. Compare it with the following about bench press. Both will give you a bigger chest and some more arm and shoulder size. Push ups work the stomach more. I've been working out in the gym for more than 40 years. My advice to anyone who will listen is to do a lot of push ups. Yes, I know the bench will get you stronger than push ups, but it is push ups that will allow you to bench when you get my age.