for a finite group $g$ and a subgroup $h$ of $g$, the relative commutativity degree of $h$ in $g$, denoted by $d(h,g)$, is the probability that an element of $h$ commutes with an element of $g$. let $mathcal{d}(g)={d(h,g):hleq g}$ be the set of all relative commutativity degrees of subgroups of $g$. it is shown that a finite group $g$ admits three relative commutativity degrees if a...