(a) Discount amount = Face value - Price of t-bills = $1,000-$996 = $4
(b) Amount received at maturity = Face value = $1,000 (Note: T-bills are guaranteed and thus one of the safest investment).
(c) Current yield, R = Discount amount/Face value * 360/t, where t = 52 weeks = 360 days.
Then,
R = (4/1000)*(360/360)*100 = 0.4%