Simulate a postage stamp vending machine. A customer inserts dollar bills into the vending machine

and then pushes a $$purchase$$ button. The vending machine gives out as many first$-$class stamps as

the customer paid for, and returns the change in penny $($one$-$cent$)$ stamps. A first$-$class stamp cost

$49$ cents. $($Tip: recall the modulus operator$).$