Four-digit numbers

The numbers 1,2,3,4,5 are given.
Role:

a) how many 4-digit numbers can we create if the digits cannot be repeated?
b) how many generated numbers will not contain the digit 1?
c) How many of the generated numbers will be divisible by 5?
d) How many of the generated numbers will be even?

Final Answer:

a =  120
b =  24
c =  24
d =  12

Step-by-step explanation:

$a=5\cdot 4\cdot 3\cdot 2=120$

$b=4\cdot 3\cdot 2\cdot 1=24$

$c=4\cdot 3\cdot 2\cdot 1=24$

$d=3\cdot 2\cdot 1\cdot 2=12$

Try another example