Part a: the sun produces 3.9 ⋅ 1033 ergs of radiant energy per second. how many ergs of radiant energy does the sun produce in 2.45 ⋅ 105 seconds? express your answer in scientific notation and show your work. (5 points)

part b: which is the more reasonable measurement of the distance between the tracks on a dvd:
7.4 ⋅ 10−4 mm or 7.4 ⋅ 104 mm? justify your answer. (5 points)