5 mm -diameter sphere is charged to -4.6 nC . An electron fired directly at the sphere from far away comes to within 0.39 mm of the surface of the...

A 2.5 mm -diameter sphere is charged to -4.6 nC . An electron fired directly at the sphere from far away comes to within 0.39 mm of the surface of the target before being reflected. Part A What was the electron's initial speed? Part B At what distance from the surface of the sphere is the electron's speed half of its initial value? Part C What is the acceleration of the electron at its turning point?