Refer to the above table. Suppose that demand is represented by columns (3) and (1) and supply is represented by columns (3) and (4). If regulators set a price ceiling at $7, A. the market would clear. B. a shortage of 50 units would occur. C. demand would change from columns (3) and (1) to columns (3) and (2). D. a surplus of 50 units would occur.