You prepare $4-$ethyl$-5,6-$dimethyl$-2-$heptanol from an unsaturated hydrocarbon by acid catalyzed hydration.

a$)$ Present a reaction equation that shows the structural formulas of organic compounds and the necessary reagents.

b$)$ Present the detailed reaction mechanism, i$.$e$.$ the arrows describing the movement of electrons, and the structures of the compounds occurring in the reaction.

c$)$ Justify the choice of unsaturated hydrocarbon and reagent. Tell what kind of intermediate step the reaction goes through, and why it happens.

d$)$ Point out the electrophiles and nucleophiles in the different stages of the reaction.