Deteremine the failure rate for the following: 50 light bulbs were tested for 500 hours. 12 light bulbs failed at 30 hours, 4 light bulbs failed at 60 hours, another 4 failed at 75 hours, 5 failed at 160 hours and 2 failed at 370 hours. The remaining light bulbs completed the 500 hour test satisfactorily.