See attached pictures: 1960 house (Plumbing novice) I discovered a 4-5” hairline crack on the bottom of the 4” copper waste pipe where it connects to the rubber coupling that is transitioned to PVC that goes to the toilet flange that has a slow drip leak. This copper runs a short distance where it T’s into the main stack. What’s the best way to attack this (replace everything to the T or see if I can salvage some of that existing copper line half way? Is there a coupling I could use to attach to the T fitting on the stack and use PVC for the rest of the run?