Problem: The center of a 1.30 km diameter spherical pocket of oil is 1.30 km beneath the Earth's surface. Estimate by what percentage g directly above the pocket of oil would differ from the expected value of g for a uniform Earth? Assume the density of oil is 8.10x10^3 kg/m^3 Should I use the equation: F = G (m1 + m2) / r^2 ? If not, which equation should I use? Please help me to get started. Thank you.