Answer:
The probability that the pen will last at least 440 days is 0.1587
Explanation:
Given that
Mean = μ = 400 days
SD = σ = 40 days
Now we have to find the probability of a data point X = 440
For that first of all we have to find the z-score of the value
z-score is found using the formula

Putting the values of x, mean and SD we will get,

At least 440 means that either 440 or greater than this, hence, we have to find area to the right of z=1
For that

Hence,
The probability that the pen will last at least 440 days is 0.1587