\text { Complete the following redox reaction, where } \mathrm{X} \text { is } \mathrm{H}_{2} \mathrm{O}, \mathrm{NCS}^{-}, \mathrm{SCN}^{-} \text {, and } \mathrm{I} \text {. } \left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{X}\right]^{2+}+\left[\mathrm{Cr}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{2+} \rightarrow

? Answer the following questions: (а)propose the reaction mechanism, (b)suggest the order of the rate of reaction, and (c)explain the variation in the rate of reaction.