Final answer:
The pattern can be explained by the fact that bond U is callable and bond V is non-callable.
Step-by-step explanation:
The pattern of the lower-rated bond (bond V) offering a lower benchmark spread than the higher-rated bond (bond U) can be explained by the fact that bond U is callable and bond V is non-callable.
When a bond is callable, it means that the issuer has the option to redeem it before the maturity date. Callable bonds are typically issued with a higher coupon rate to compensate investors for the risk of early redemption. This higher coupon rate leads to a higher benchmark spread.
On the other hand, non-callable bonds do not have the risk of early redemption, so they are issued with a lower coupon rate. This lower coupon rate results in a lower benchmark spread compared to callable bonds.