Electric lines of force

1.) Two +ve charges Q and 4Q are fixed at distance 12cm. Sketch lines of force and locate null point.

2.) Two point charges q and 4q are kept at a distance r from each other. While showing electric line plot indicate the neutral point by calculating its position value.

3.) Metallic and then dielectric slab is introduced b/w the plates of a charged || plate capacitor. Sketch lines of force b/w the plates.

4.) If a charge +q is fixed at 'x' distance in front of an infinte metal plate, draw electric lines of force and explain.

don't know how to sketch lines and how will I get null point??????????