The equilibrium gap when machining $($electro$-$chemically$)$ iron using sodium chloride solution in water as the electrolyte, is found to be $0\mathrm{.}25$ mm with an operating voltage of $18$ volt. Iron dissolves at a valency of $2.$ The specific resistance of the electrolyte is $2\mathrm{.}8$ ohm$-$cm$.$ Calculate the metal removal rate per unit surface area, if the feed is applied at an angle of $15$ to the normal of the work piece. Take the over voltage as $1\mathrm{.}5$ V$.$