The radioactive isotope $^{238} \mathrm{Pu},$ used in pacemakers, decays by emitting an alpha particle with a half-life of 86 yr. (a) Write an equation for the decay process. (b) The energy of the emitted alpha particle is $9.0 \times$ $10^{-13} \mathrm{J},$ which is the energy per decay. Assuming that all the alpha particle energy is used to run the pacemaker, calculate the power output at $t=0$ and $t=10$ yr. Initially $1.0 \mathrm{mg}$ of $^{238} \mathrm{Pu}$ was present in the pacemaker. (Hint: After 10 yr, the activity of the isotope decreases by 8.0 percent. Power is measured in watts or J/s.)