A door can be opened only with a security code that consists of five buttons: 1, 2, 3, 4, 5. A code consists of pressing any one button, or any two, or any three, or any four, or all five.
How many possible codes are there? (You are to press all the buttons at once, so the order doesn't matter.) If, to open the door you must press three codes, then how many possible ways are there to open the door? Assume that the same code may be repeated.