Incandescent lamp 3 yuan.
Set two boards to work for x hours at the same time.
3+0.5 times 0.06x=60+0.0 1 times 0.5x.
It is concluded that it is more cost-effective to use energy-saving lamps for more than 2280 hours than incandescent lamps, because the service life of energy-saving lamps is more than 3000 hours.