I will just answer the problem about Pin numbers because the other questions lack other given values.
a. How many different pin numbers are there?
There are 26 letters in total and 10 numbers in total (including zero), therefore the total number of different pin numbers are:
Total possible = 26 * 26 * 10 * 10 * 10
Total possible = 676,000 different pins
b. What is the probability a pin number selected at random ends in 000
The total possible numbers with ending of 0 0 0 is:
Possible numbers = 26 * 26 * 1 * 1 *1
Possible numbers = 676
Therefore the probability is:
Probability = 676 / 676,000
Probability = 0.001 = 0.10%
c. What is the probability a pin number selected at random begins with AA?
The total possible numbers starting with A A is:
Possible numbers = 1 * 1 * 10 * 10 * 10
Possible numbers = 1000
Therefore the probability is:
Probability = 1000 / 676,000
Probability = 1.48 x 10^-3 = 0.148%