Question 120
We must choose a seven-character password that contains at least one letter and at least one digit. We may choose among the characters $A, B, C, G, J, M, R, Z$ and $3$.
a) How many possible choices of password are there if the characters may not be repeated?
b) How many possible choices of password are there if the characters may be repeated?
a) How many possible choices of password are there if the characters may not be repeated?
b) How many possible choices of password are there if the characters may be repeated?