Answer:
U = - 4 x [tex]10^{-10}[/tex]
Explanation:
ΔV = potential difference = [tex]2.5 * 10^9[/tex] Volts
q = charge on electron = [tex]-1.6 * 10^{-19}[/tex] C
electric potential energy is given as
U = q ΔV = ( [tex]-1.6 * 10^{-19}[/tex]  ) ( [tex]2.5 * 10^9[/tex]  )
        = - 4 x [tex]10^{-10}[/tex]