Use truth tables to obtain the answers to the following exercises:
Two astronomers are discussing supernovas. Dr. Frank says, "Research has established that if a supernova occurs within ten light-years of the Earth, then life on Earth will be destroyed." Dr. Harris says, "Research has also established that either a supernova will not occur within ten light-years of the Earth or life on Earth will not be destroyed." Is it possible that both astronomers are correct? If so, what can we determine about the occurrence of a supernova?