The Post Office down the road has run out of all stamps except 3c and nc stamps, where n is any whole number. They have a large amount of each of these. The post master isn’t too worried though. He tells the person on the counter that he can make up every amount from (2n – 2)c onwards. Is that right? Can you justify it or can you find an amount of postage bigger than (2n – 2)c that the Post Office can’t make up?
