Evaluate the amount of heat produced during a day by a --active Na24 preparation of mass m

Question:

Evaluate the amount of heat produced during a day by a β--active Na24 preparation of mass m = 1.0 rag. The beta-particles are assumed to possess an average kinetic energy equal to 1/3 of the highest possible energy of the given decay. The half-life of Na24 is T = 15 hours.