Astronomers using a 2.0-m-diameter telescope observe a distant supernova−an exploding star. the telescope's detector records 7.5 × 10−11 j of light energy during the first t s. it's known that this type of supernova has a visible-light power output of 6.0 × 1037 w for the first 10 s of the explosion. how distant is the supernova? give your answer in light years, where one light year is the distance light travels in one year. the speed of light is 3.0 × 108 m/s.