An image of a rectangular pyramid is shown below: A right rectangular pyramid is shown.

Part A: A cross section of the rectangular pyramid is cut with a plane perpendicular to the base, passing through the top vertex. What is the name of the shape created by the cross section? Explain your answer. (5 points)

Part B: If a cross section of the rectangular pyramid is cut perpendicular to the base, but not passing through the top vertex, what would be the shape of the resulting cross section? Explain your answer. (5 points)