A 60-watt outdoor lightbulb is advertised as having an average life (i.e. MTTF) of 1,000 operating hours. However, experience has shown that it will also fail on demand an average of once every 120 cycles. A particular bulb is turned on once each evening for an average of 10 hours. If it is desired to have a reliability rate of 90 percent, what is its design life in days (assuming it follows a constant failure rate)?