If the Total Energy of an Electron in an Accelerator

Multiple Choice

If the total energy of an electron in an accelerator is three times its rest energy,what is its speed? (c = 3.00 × 10⁸ m/s)

A) 2.00 × 10⁸ m/s
B) 1.30 × 10⁸ m/s
C) 1.41 × 10⁸ m/s
D) 2.98 × 10⁸ m/s
E) ​2.83 × 10⁸ m/s