Two identical charges, both labeled q1 in the diagram, are placed on the x axis at (−a,0) and ( a,0) . The electric field is observed at point P , located on the y axis at (0, a) . Charge q2 is added at the origin so that the net electric field at the observation point P is zero. If q1= 6.5μC and a= 4.4 m, what is the value of charge q2 , in microcoulombs?