Circle enclosing the convex hull of $n$ points

Question

Suppose $P_1,P_2,,\cdots,P_n$ aren points inn the plane with given centriod $C=(a,b)$and $$d=\text{max distance}(P_i,P_j),i \neq j$$.Can we find a circle of some radius and center in terms of $d$ and $a$ and $b$ which contains the convex hull of the given points?
Any hints/suggestions are highly appreciated.