To answer this question remember that the definition of an electric field potential is based on the amount of work that is required to move a charge q from one point to another. So your work A = q(Va - Vb). The problem statement says that the potential difference Va - Vb is 2000J/C.
Note, that J is a unit of energy, not a potential difference. Joules/Coulomb is another way to say Volt. So if you meant a potential difference of 2000 Volts, then this answer makes sense. Otherwise, the question needs to make more sense.
Also, note that it doesn't matter if the charge travels in a straight line, or takes a meandering path to arrive at the destination point. An electric field is a conservative field, which means that the energy used to get from one point to the other is independent of path.
A = q*2000 = 4.6e-6 [J/C] * 2000 [C] = 9.2e-3 J