A satellite must experience an acceleration due to gravity equal to 0.90g of the Earth’s surface value. Simultaneously, inside a vertical shaft dug into Earth, there is a depth where the acceleration is also 0.90g. Which pair of altitude h and depth d (both in km) satisfies this condition? (Take Earth’s radius R=6400km.)
(a) h≈640km,d≈350km
(b) h≈350km,d≈640km
(c) h≈350km,d≈350km
(d) h≈320km,d≈640km