3. It is not the case that either the earth’s molten core is stationary or that it contains no iron. If it is not the case that both the earth’s molten core is stationary and has a regular topography, then either the earth’s core contains no iron or the direction of the earth’s magnetic fi eld is subject to change. Th erefore, the direction of the earth’s magnetic fi eld is subject to change. (S, C, R, D) Translate the following arguments into symbolic form and then use the fi rst thirteen rules of inference to derive the conclusion of each. Use the translation letters in the order in which they are listed.