Answer :
Answer:
(a) 750 codes
(b) 180 codes
Step-by-step explanation:
The number of possible access codes is given by the number of ways to pick 3 out of 5 buttons added to the number of ways to pick 4 out of 5 buttons, in which the order matters.
(a) If a button may be repeated.:
[tex]n=5*5*5*5+5*5*5\\n=750\ codes[/tex]
There are 750 possible codes.
(b) If a button may not be repeated.
[tex]n=5*4*3*2+5*4*3\\n=180\ codes[/tex]
There are 180 possible codes.