If $R ^ { f f }$ Is the Federal Funds Rate, R Is the Market Interest

If $R ^ { f f }$ is the federal funds rate, R is the market interest rate, and $\bar { f }$
Is the financial friction, what is the equation for the market interest rate?

A) $R = R ^ { f f } + f$
B) $R = R ^ { f f } - \bar { f }$
C) $R ^ { f f } = R + \bar { f }$
D) $R = R ^ { f f } ( 1 + \bar { f } )$
E) $R = R ^ { f f } \times \bar { f }$