The number of permutations of the 25 letters taken 2 at a time (with repetitions) is:

The number of permutations of the 9 digits taken 4 at a time (with repetitions) is:

Each permutation of letters can be taken with each permutation of digits, therefore the total number of possible passwords is:
Answer:
Multiply the first two binomials: (x+2) & (x+4) using the FOIL method (First, Outer, Inner & Last).
(x+2)(x+4) = x^² + 4x + 2x + 8 = x^² + 6x + 8
Then we multiply the trinomial that we got from the first stage and multiply that by the remaining binomial:
(x^² + 6x + 8) (x + 4)
= x^³ + 4x^² + 6x^² + 24x + 8x + 32
Collect the like terms together to give you:
x^³ + 10x^² + 32x + 32
Answer:
A
Step-by-step explanation:
3 weeks x 110 minutes = 330 minutes
330 minutes a week x 14 weeks = 4620 minutes
4620 divided by 60 minutes = 77 hours
77 hours is your answer