In an effort to reduce energy costs, a major university has installed more efficient lights as well as automatic sensors that turn the lights off when no movement is present in a room. Historically, the cost of lighting an average classroom for $1$ week has been $$265.$ To determine whether the changes have significantly reduced costs, the university takes a sample of $100$ classrooms. They find that the average cost for $1$ week is $$249$ with a standard deviation of $$78.$ When testing the hypothesis $($at the $1\%$ level of significance$)$ that the average energy use has decreased from the past, what is the critical value? $($please round your answer to $2$ decimal places$)$