1. Prove that Nikki can pay me exactly 4USD in value, through only the exchange of 5NZD and 5USD bills. 2. In Exercise 7.62, was there something special about the number 4? Identify for which...

1. Prove that Nikki can pay me exactly 4USD in value, through only the exchange of 5NZD and 5USD bills.

2. In Exercise 7.62, was there something special about the number 4? Identify for which nonnegative integers x Nikki can pay me back exactly x USD in value, through only the exchange of 5NZD and 5USD bills, and prove your answer