36. For convenience, astronomers often use astronomical units (AU) to measure distances within the solar system. One AU equals the average distance from Earth to the sun. Halley's Comet returns once every 75.3 years. What is the average radius of the orbit of Halley's Comet in AU)
a. 0.002 AU
b. 0.056 AU
c. 17.8 AU
d. 653 AU
