Help with shaded area fraction

Will give brainlist

Cassie is traveling 675 miles today to visit her brother and his family. so far, she has stopped for gas three times. at the first stop, she put in 7.1 gallons of gas and paid $23.79. at her second stop, she put in 5.8 gallons of gas and paid $19.08. and, at the third stop, 6.6 gallons and paid $20.39. at which stop did casey pay the most for gas?

Asphere has a diameter of 10 in. what is the volume of the sphere?

The radius of the earth is two times the radius of the moon. what fraction of the volume of the earth is the volume of the moon?