The orbit of the planet Venus is nearly circular with an orbital velocity of 78.3 3 × 103 mi/h. Knowing that the mean distance from the center of the sun to the center of Venus is 67.2 × 106 mi and that the radius of the sun is 432 × 103 mi, determine

(a) The mass of the sun,

(b) The acceleration of gravity at the surface of the sun.