PLEASE HELP! I WILL MARK THE BRAINLIEST IF YOU HAVE THE CORRECT ANSWER!! When Sandy and Allen's mother decorates the house for a holiday by herself, it takes her 5 hours. When both Sandy and Allen help, the three can finish the job in 2.5 hours. When only Allen helps his mother decorate, it takes the two 3.5 hours. How long would it take Sandy to decorate the house by herself?