Long description

The figure consists of four parts and eight horizontal blocks.

Part "a": The block labeled before X terminates contains 3 sections labeled A, X, B becomes the block labeled After X terminates containing 3 sections labeled A, blank (shaded), B.

Part b: The block labeled before X terminates contains 3 sections labeled A, X, blank (shaded) becomes the block labeled After X terminates containing 2 sections labeled A, blank (shaded).

Part c: The block labeled before X terminates contains 3 sections labeled blank (shaded), X, B becomes the block labeled after X terminates contains 2 sections labeled blank (shaded), B.

Part d: The block labeled before X terminates contains 3 sections labeled blank (shaded), X, blank (shaded) becomes the block labeled After X terminates which is completely shaded.