Answer:



Step-by-step explanation:
Given
Let
A = Event of being a universal donor.
So:


Solving (a): Mean and Standard deviation.
The mean is:



The standard deviation is:




Solving (b): P(x = 3)
The event is a binomial event an dthe probability is calculated as:

So, we have:




Answer:
620
Step-by-step explanation:
selling 400 doughnuts means selling 800 £ worth of doughnuts. 800 x 0.4 ( to find 40 percent) = 320, + 300 because the the fixed cost = 620. :)
It would cost 2.50$ for each shirt.