National Electirc Code?

I've have 4 questions on working with branch circuits. 1) You're working in a house that operates on 240 volts and the oven is on a branch circuit by itself, what is the demand load for this circuit? 2) What size TW copper conductor should be used for it? 3) You're working in a kitchen that contains a 8Kw counter mounted range and 2 wall mounted 6Kw ovens that has all 3 units on the same 240v branch circuit, what would be the demand load? And What minimum size TW copper conduits should be used? 4) What would be the demand load for all of these items? Please show me step by step on hoe to solve the problem.