Software availability is the probability that a program is operating at a given point in time
Given time period 365 days each day has 1440 minutes
so total time in minutes =365x1440=525600
Non working time =20x2 =40 minutes (20 times failed each time it took 2 min to restart)
Software availability = 525560 / 525600 = .999924 or 99.9924 %
Hence option 4 is right ans