Two point charges are fixed on the x-axis: Q1=+6.0μC at x=−0.30m and an unknown charge Q2 at x=+0.30m. A sensor located at the point (0,0.40m) measures an electric field of 3.5×105N/C directed straight upward (positive y-direction). Which of the following is closest to the value of Q2?
a) +12μC
b) −6μC
c) +6μC
d) +3μC