Dbl - either takeout or exactly 3 hearts, depending upon agreements. Takeout in SAYC 1NT - 18-19 Pass - minimum, 3-5♣ including all 12-14 balanced with a doubleton heart and some with three hearts - why would you bid again on these hands? Having said that, I'm not sure if this is SAYC or not. Playing 12-14 NT, you need to act again on 15-17 bal, either with a double or 1NT. If 1NT, you have to decide what you will do with no stopper in the opps suit.