For this, we need the formula:
V = k q / r
where k is the Coulombs law constant = 9 x 10^9 N
q is the charge of the hydrogen nucleus (proton) = <span>1.6 x 10^-19 C</span>
r is the distance
Simply plug in the values and solve for V
An example of something that is not a proton would be an electron. It has a negative charge and has a charge of 1.6X10^-19 Coulombs.
Velocity is distance over time

. If it wants it in km/h you're good to go otherwise if its m/s you need to convert km to m by multiplying 30 by 1000 and t in hours to seconds by multiplying 0.5 by 3600.
I think it should be option (b)