Final answer:
The liquidity premium on the four-year Treasury security is 0.25% or 25 basis points.
Step-by-step explanation:
According to the Liquidity Premium Theory, the liquidity premium on a bond is the additional interest rate investors require in exchange for holding a less liquid security.
In this case, the liquidity premium on the four-year Treasury security can be calculated by subtracting the three-year Treasury rate from the four-year Treasury rate. Therefore, the liquidity premium on the four-year Treasury security is 5.50% - 5.25% = 0.25% (or 25 basis points).