A tortfeasor who made a settlement with a claimant releasing all tortfeasors from their liability for an accident was entitled to contribution from the other tortfeasors.  A Superior Court Judge allowed the defendants' motion for dismissal pursuant to Mass.R.Civ.P. 12(b) (6), 365 Mass. 755 (1974), in an action in which the plaintiffs sought contribution for sums paid by them in settlement of claims arising from an automobile accident. The single issue presented is whether one of two or more joint tortfeasors who enters into a settlement with a claimant which releases all tortfeasors may recover contribution from the other wrongdoer(s) under G. L. c. 231B.