An insurance company relies heavily on an EDP IT system for claims' processing. So they invested in a backup system. There are three modules in the system which must all function for the system to function. The backup system has identical modules as the main system. The first module reliability of the system is 0.88, the second module reliability is 0.87 and the reliability of the third module is 0.83. What is the overall reliability of the EDP systems taking into consideration the backup system?