Answer: B) 115 pounds
Step-by-step explanation:
Because x is the number of days passed, after 21 days, x = 21.

Hope it helps <3
The normal distribution curve for the problem is shown below
We need to standardise the value X=405.5 by using the formula


We now need to find the probability of z=0.32 by reading the z-table
Note that z-table would give the reading to the left of z-score, so if your aim is to work out the area to the right of a z-score, then you'd need to do:

from the z-table, the reading

gives 0.6255
hence,

The probability that the mean weight for a sample of 40 trout exceeds 405.5 gram is 0.3475 = 34.75%
Printer A prints for 10 minutes, so prints
... (30 pages/minute)×(10 minutes) = 300 pages
Printer B prints for 7 minutes, so prints
... (40 pages/minute)×(7 minutes) = 280 pages
At the end of 10 minutes, the two printers will have printed
... 300 pages + 280 pages = 580 pages