In July 2016 I purchased three apps: Calculus Made Easy; Physics Made Easy and Chemistry Made Easy. These were installed on a ti89 calculator used by my granddaughter who is a university freshman. She has reported that the apps have been very helpful and easy to use. I was very impressed by the level of support that Mike provided me. His responses were timely; his suggestions and guidance were clear and included step by step procedures. This is an exceptional level of customer support and I will continue to purchase "Made Easy" products as my granddaughter continues her education. William S.K.