The pound sign is supposed to be a <=, the computer mess up, and the x is supposed to be a t in 0 <= t <= 8. I need help with the under or overestimate on problem c and all of problem d. Thank you

Select the correct answer. what was edwin hubble's contribution to the field of astronomy? a. he discovered variable stars. b. he proved that the heliocentric model accurately described our solar system. c. he found a relationship between the period luminosity and distance of stars. d. he proved that the universe is finite. e. he discovered that the universe was expanding.