4. NASA's Mars rover, similar to outer solar system probes like Voyager or Cassini, uses an RTG (Radioisotope-Thermal-Generator) to produce the electric energy for the rover. It utilizes thermoelectric generators to transform heat from the radioactive decay into electric energy. a) What is the activity (in Bq) of 1Kg 238 Pu? The half-life time of 238 Pu is 88 years. b) What is the heat this 1kg produces per second? 238 Pu decays to 100 % by alpha decay with a kinetic energy of 5.6 MeV of the alpha particles. Assume that this kinetic energy is the sole source for the heat. c) Assuming an efficiency of 10%, i.e. 10% of the heat is transformed into electrical energy, what amount of 238 Pu (in kg) is needed to produce 2.2KWh of electrical energy over one day? d) By how much (in percents) will the generated heat decrease after 10 years if only the decay of the original 238 Pu is taken into account