The cakes have to be made in batches. Therefore for maximum demand they will have to make 140/40 = 4 batches of Brownies (they can’t make part batches); 90/30 = 3 batches of Muffins, and 100/20 = 5 batches of Cupcakes.
Therefore the time needed in baking for maximum demand is (4 x 120) + (3 x 110) + (5 x 120) = 1,410 minutes. There are 1,440 minutes available, so baking is not a bottleneck.