The weekly incomes of shift foreman in a glass industry follow the normal probability distribution with a mean of $1000 and standard deviation of $100.

a. What is the z value for the income, let's call it X, of a foreman who earns $1,100 per week? For a foreman who earns $900 per week?

b. What is the likelihood of selecting a foreman whose weekly income is between $1000 and $1100?

c. What is the probability of selecting a shift foreman in the glass industry whose income is between $790 and 1000?

d. What is the probability of selecting a shift foreman in the glass industry whose income is less than $790?