# Requirement change

Marketing has signed off on the summer promotion and it goes live now. Two things.

**Everything is a fifth off.** Take the shelf price, knock 20% off it, and then round the result
*down* to the nearest 5 so we are not handing out prices ending in odd cents. So the chips at 65
become 50 — 20% off 65 is 52, and 52 rounds down to 50. The chocolate at 100 becomes 80. The gum
at 25 becomes 20.

**The water is free.** All of it, slot B2, no charge. It has been a hot summer and the goodwill is
worth more than the revenue.

A few things I want to be clear about, because they have caught us out before:

- The **shelf labels do not change.** If you ask the machine what is in slot A1 it still says the
  price is 65, because that is what is printed on the rack. The discount is what the till charges.
  The receipt should show what the customer actually paid.
- Everything else follows from the price the customer actually pays. If they put a dollar in for
  the chips they get 50 back, not 35. If they put a quarter in they are still 25 short, not 40.
- Because the water is free, a customer can just press B2 without putting anything in at all, and
  they should get their water. If they *did* put money in first, they get all of it back as change.
- Nothing else moves. Same stock, same states, same refusals, same coins. A sold-out slot is still
  sold out however cheap it has become, and the machine still will not sell anything it cannot
  change.
