I am installing a new shower in my basement. It has a concrete subfloor and the drain is roughed in for a tub. I am installing ceramic tile on the floor and walls. I have three questions. First, at what height do I install the drain if I do not know the finished height of the tile? Second, how much of a slope is required for a shower floor 32" wide by 48" long? Lastly, should I install a liner if the subfloor is concrete? Thanks in advance for your advise.