You are responsible for a system being funded by the NSA's to monitor for alien mind control rays. There are 12 independent monitoring systems equipped with the proper tinfoil hats with a mean time between failure of 2000 hours supporting the system operations. If one must be in operation at all times over a 24 hour period to detect these mind rays, what is the minimum number of these monitoring systems that must be left in operation to maintain at least a 99.99% probability of success?