Find the Cartesian form of the equation of the straight line l1 which passes through the point p=(2,3,0) and q=(0,1.2).

Find also the Cartesian form of the equation of a straight line l2 which passes through p, is perpendicular to l1 and parallel to the plane Oxy.

I have done the first part by using the equation of a straight line passing from two points, but for part b I don't know how to deduce it. Any help would be appreciated!