PLEASE HELP WILL GIVE BRAINLIEST

Step-by-step explanation:

I may get this wrong because I don't think it's clear enough.

3 Letters

The station call letters must start with 1 of 3 letters

3

The next letter must be one of 25 and the last letter is 24

3 * 25 * 24 = 1800

5 letters

3 * 25 * 24 * 23*  22 = 910800

Total 1800 + 910800 = 912600

yes because there is exactly one y value for every x value

for function there can't be more than one value for every x value