American Express Business Travel uses a ten-letter record locator number (RLN) for each client's trip (e.g., KEZLFSRQMP). (a) How many different RLNs can be created using capital letters (A to Z)?

(b)What if it allows any mixture of capital letters (A to Z) and digits (0 to 9)?

(c)What if it allows capital letters and digits but excludes the digits 0 and 1 and the letters O and I because they look too much alike?