Consider the precipitation of a spherical B$-$rich phase $(\backslash$beta phase$)$ from a dilute solution $(\backslash$alpha phase$)$ of B in A$.$ Suppose the original concentration of B in the solid solution is C$\_(0)=5\backslash$times $10^(21)$ atoms $/$cm$^(3),$ the diffusion coefficient of B is D$=2\backslash$times $10^(-10)$c$($m$^(2))/($sec$),$ and the interface transfer parameter of B is M$=2\backslash$times $10^(-6)$c$($m$)/($sec$).$ The equilibrium concentration of B in the $\backslash$alpha and the $\backslash$beta phases and $($:C$\_(\backslash$beta $)$