How do I get part a and b

(25 pts) The Lazy Susan from the previous problem is rotating at 1.48 rad/s when Rycell sets a two-liter of Coke (m = 2.15 kg) on it, 0.175 m from the center. a) What is the initial angular momentum of the Lazy Susan before the Coke is set on it? b) What is the rotational speed of the Lazy Susan after she drops the Coke on it? Cok