Emma wants to calculate the mean time between failures for a device in her organization. How should she calculate the MTBF? Emma wants to calculate the mean time between failures for a device in her organization. How should she calculate the MTBF? The total number of operational hours divided by the number of failures during that time period The number of failures that have occurred in one year divided by 365 The average number of failures per day divided by the number of days the company is open per year The annual rate of occurrence multiplied by the expected useful lifetime of the device