Calculate the acceleration due to gravity at the North Pole?

Earth is commonly thought of as a sphere, but that is not true. Because of Earth's spin, it closley resembles an oblate spheriod, which is just a fancy name for "shaped like squashed orange." The effect of this spin is a tidal bulge that forms at the equator so that the equatorial radius of earth is about 21 km greater than the polar radius of 6370 km. The m of Earth is 5.979 x 10 to the power of 24 kg. Calculate the accelerationdue to gravity at the North Pole using the definition of gravitational field.