2.5 A new unit of length is chosen such that the speed of light in a vacuum is unity. What is the distance between the Sun and the Earth in terms of the new unit if light takes 8 min and 20 s to cover this distance?

According to the problem, speed of light in vacuum, c = 1 new unit of length.
Time is taken by light to cover the distance between the sun and the earth.
t = 8 min 20 s = 500 s.
So, the distance between the sun and earth
= c x t
= 1 new unit of length x 500 s
= 500 new units of length.