A space probe launched to converge with the orbit of Pluto. Celestial bodies that are farther than Neptune and are classified as dwarf planets have been found, in addition to Pluto. We consider a space probe that is launched to the neighborhood of the orbit of Pluto. In the following discussion, it should be noted that all objects, including planets, revolving around the Sun obey Kepler's laws.
(1) In accurate terms, the orbit of the Earth is an ellipse, but it is approximately a circle. The radius of this circle is the astronomical unit. Pluto's semimajor axis is about 40 astronomical units. What is Pluto's orbital period? Choose the best values from the following (a) through (f).
(a) 10 years
(b) 40 years
(c) 180 years
(d) 250 years
(e) 640 years
(f) 1600 years