An infinite line of charge per unit length is parallel to the line of intersection of

Question:

An infinite line of charge λ per unit length is parallel to the line of intersection of two infinite conducting planes set at right angles to one another, such that it is a distance a from one and b from the other. Show that this arrangement is equivalent to four line charges so far as the electric field in the quadrant containing the original line charge is concerned. Hence calculate the charge induced per unit length on each plate.