At a point in an electrostatic field the potential is 400 V. A test charge of +2 μC kept there has potential energy U₁. If the test charge is replaced by +6 μC, which of the following statements is correct?
a) U2=3U1 and the potential becomes 1200V
b) U2=U1 and the potential remains 400V
c) U2=3U1 and the potential remains 400V
d) U2=9U1 and the potential remains 400V