Given 4% Interest PV = $500 received each year for 4 years

FV = $500 invested each year for 4 years

Consider that a 10-year UST offers 4.5% return, but a 10-year AAA Corporate Bond offers 5.6% => what causes the difference of 1.1%?

Consider that a 1-year UST offers 1.2%, but a five-year UST offers 2.1% => what two influences could be causing the 0.9% difference?