Равновесная ставка процента определяется на рынке капитала с сравнения предельной прибыли на капитал

Billy is fat. He has cakes and chocolate for breakfast. He has sweets and jam for lunch. Yesterday Billy ate two box of chocolates, fifteen pieces of cake and ten bags of sweets. He doesn`t eat cabbage and carrots. Billy doesn`t like to run and jump. He can`t swim. Billy is sad. Can you help my friend Billy?