In determining the proportionate share of the shared liability between two (2) or more tort-feasors for the same injury or wrongful death, for purposes of pursuit of contribution among tort-feasors:
(1) The reasonable amount of the settlement and the relative degree of fault of the tort-feasors and the injured party or parties in bringing about the injury or wrongful death shall be compared, and the party seeking contribution shall be entitled to recover only to the extent that the party has paid more than the proportionate share of the common liability, with the proportionate share to be determined solely by comparison of the relative degrees of fault of the parties;
(2) If equity requires, the collective liability of some as a group shall constitute a single proportionate share; and
(3) Principles of equity applicable to contribution generally shall apply.