Interpolated Spreads

Can anyone help me make sense of this problem. How does Bond X have the lowest G spread?

Exhibit 2

Comparative Analysis of Transportation Sector Bonds

Bond X Y Z
Effective duration 12.4 9.1 10.1
Benchmark spread 125 125 125

Swanson makes the following notes:

  • The three transportation sector bonds
    • have the same spread as the on-the-run 10-year US Treasury,
    • are priced near par value, and
    • have roughly equivalent underlying credit risk.
  • The yield curve is currently upward sloping.

For valuation reasons, Swanson plans to sell the bond with the lowest G-spread.