A GaAs single crystal is grown by the Bridgman technique for production of p$-$type GaAs wafers doped with $0\mathrm{.}6$ ppm Mg$.$ The equilibrium partition coefficient of Mg is $0\mathrm{.}1.$ Determine the effective segregation coefficient that at least $65\%$ of the single crystal is within $0\mathrm{.}05$ ppm of the $0\mathrm{.}6$ ppm target value when the melt contains $0\mathrm{.}65$ ppm Mg$.).$