A sphere is inscribed inside a cube with edges of 6 cm. In cubic centimeters, what is the volume of the sphere in terms of ?

Martha is training for a duathlon, which includes biking and running. she knows that yesterday she covered a total distance of over 55.5 miles in more than than 4.5 hours of training. martha runs at a speed of 6 mph and bikes at a rate of 15.5 mph.