Two positive charges, each of magnitude q, are on the y-axis at points y=+a and y=-a. where would a third positive charge of the same magnitude be located for the net force on the third charge of the same magnitude be located for the net force on the third charge of the same magnitude be located for the net force on the third charge to be zero?

A.) at the origin

B.) at y=2a

C.) at y=-2a

D.) at y=-a