A Thin Glass Rod Is Bent into a Semicircle of Radius

Multiple Choice

A thin glass rod is bent into a semicircle of radius R.A charge + Q is uniformly distributed along the upper half,and a charge -Q is uniformly distributed along the lower half,as shown in the figure.If R = 10 cm and the electric field E at point P is 4.81 * 10⁴ N/C in -y direction,what is the charge,Q? Point P is at the center of the semicircle.

A) 62 nC
B) 10 nC
C) 42 nC
D) 27 nC
E) 51 nC