Here is the question?

1.The owner of a fish market has an assistant who has determined that the weights of catfish are normally distributed, with mean of 3.2 pounds and standard deviation of 0.8 pound. What percentage of samples of 4 fish will have sample means between 3.0 and 4.0 pounds?

a)84%

b)67%

c)29%

d)16%

I need to now the steps in setting up this problem? how do you decide which probability formula it will use. What signs to look for? etc.