Suppose a finance student purchased a three-month T-bill with a $5,000 par value for $4,500 and sold it ninety days later for $4,200. What is the

Suppose a finance student purchased a three-month T-bill with a $5,000 par value for

$4,500 and sold it ninety days later for $4,200. What is the yield?

b. Newly issued three-month T-bills with a par value of $9,000 sold for $8,600. Compute the T-bill discount.

c. Assume that your friend paid $89,000 for a $90,000 T-bill maturing in 120 days. If you hold it until maturity, what is the T-bill yield? What is the T-bill discount? 

please explain with steps