Explanation:
Let X be the mail arrival time to a department that follows uniform distribution over 0 to 60 minutes.
The probability function of X is:
f
(
x
)
=
1
60
,
0
<
x
<
60
Now, the probability that the mail arrival time is more than 40 minutes on a given day is calculated below:
P
(
X
>
40
)
=
∫
60
40
1
60
d
x
=
[
x
60
]
60
40