An electron is accelerated from rest through a potential diff erence that has a magnitude of 2.40

Question:

An electron is accelerated from rest through a potential diff erence that has a magnitude of 2.40 × 107 V. The mass of the electron is 9.11 × 10-31 kg, and the negative charge of the electron has a magnitude of 1.60 × 10-19 C.
(a) What is the relativistic kinetic energy (in joules) of the electron?
(b) What is the speed of the electron? Express your answer as a multiple of c, the speed of light in a vacuum.