Air Raid Inc. designed 20 air-conditioning systems designed for use by astronauts in the International Space Station. All of them were operated for 1,000 hours at NASA's test facility. Out of all the systems 2 of them failed during the test. One of them after 200 hours and the other after 600 hours. What is the Per Unit Failure Rate? Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer. a 0.000106 failure/unit hour b 0.000504 failure/unit hour c 0.250346 failure/unit hour d 0.0000001 failure/unit hour e 2 failures/unit hour