Suppose that the current one-year rate (one-year spot rate) and expected one-year T-bill rates over the following three years (i.e., years 2, 3, and 4, respectively) are as follows:

₁R₁=6.20%, E(₂r₁) =6.70%, E(₃r₁) =7.70% E(₄r₁)=8.20%

Using the unbiased expectations theory, what is the current (long-term) rate for four-year-maturity Treasury securities?