For a reversible reaction $$\mathbf{R}\rightleftharpoons\mathbf{P}$$, at constant temperature, both the forward and the backward reactions are first order elementary reactions with rate constants $$k_f$$ and $$k_b$$, respectively. At time zero, the concentration of $$\mathbf{R}$$ is $$[\mathbf{R}]_0$$ and the concentration of $$\mathbf{P}$$ is zero. At any given time, $$[\mathbf{R}]$$ and $$[\mathbf{P}]$$ are the concentrations of $$\mathbf{R}$$ and $$\mathbf{P}$$, respectively. If $$k_b=4k_f$$, the correct graphical representation of the reaction is