please help me understand Part 2

Instructions:

1. Calculate the percent CPU utilization for a program that processes a file of records and performs, on average, 250 machine instructions per record. It takes 1 microsecond to execute 100 instructions by the system. The time to read one record from file is 8 microseconds and the time to write one record to file is 12 microseconds. Round your answer to the nearest tenth. (25 points)

2. Consider the following lists for the uptime(s) and downtime(s) for a particular system over a 24 hr period:

uptime (hours): {5.25, 3.45, 12.67, 2.58}

downtime (hours): {0.02, 0.005, 0.01, 0.015}

Calculate the Mean Time to Failure (MTTF), the Mean Time to Repair (MTTR) and the system Availability. Round your answer(s) to the nearest tenth. (25 points)