here is the problem

The following problems require you to make some assumptions. Be sure to specify them.

What is the shortest the address on a typical letter could be, if it is to get to a unique human recipient? (Assume the permitted characters are A-Z, 0-9). Explain your assumptions and show your work. You will need a calculator that can do logarithms.

Please, help - I don't even understand what logs would have to do with this problem.

Thanks, Vertica