412.1 Contribution Sought by Cross-Claims Between Defendant Tortfeasors in Injured Party's Original Action [This instruction should follow 506.10, Joint Liability of Joint Tortfeasors.] Even though any damages you award (claimant) must be found in a single amount against the defendant or defendants whom you find to be liable to (claimant), if the greater weight of the evidence shows that more than one defendant was negligent and that their negligence contributed as a legal cause of injury and damage to (claimant), you should determine by your verdict what percentage of the total negligence of [both] [all] defendants (name them) was caused by each.