1)7Be decays with a half-life of about 53 d. It is produced in the upper atmosphere, and filters down onto the Earth's surface. If a plant leaf is detected to have 300 decays/s of 7Be, how many days do we have to wait for the decay rate to drop to 13.6/s?

Question

1)7Be decays with a half-life of about 53 d. It is produced in the upper atmosphere, and filters down onto the Earth's surface. If a plant leaf is detected to have 300 decays/s of 7Be, how many days do we have to wait for the decay rate to drop to 13.6/s? 
2) What is the energy of the alpha particle emitted in the decay 232U ==> 228Th + alpha ?