During heaton company's first two years of operations, it reported absorption costing net operating income as follows:

For a firm that uses the weighted average method of process costing, which of the following must be true? (a) physical units can be greater than or less than equivalent units. (b) physical units must be equal to equivalent units. (c) equivalent units must be greater than or equal to physical units. (d) physical units must be greater than or equal to equivalent units.