5. (a) Show that the gravity anomaly of an infinitely long horizontal cylinder of radius R with anomalous density Ap buried at depth b beneath the surface is Ag = 2GR Apb x+b where x is the horizontal distance from the surface measurement point to the point on the surface directly over the cylinder axis. (10 points) (b) What is the maximum gravity anomaly caused by a long horizontal underground tunnel with a 10-m radium driven through rock of density 2800 kg -3 m if the axis of the tunnel lies 50 m below the surface? (10 points)