In deciding whether work is SGA, we may consider all pertinent facts about the individual's
            work, such as the nature of the duties, hours worked, productivity, pay, and any other
            factors related to the value of the services. Usually, the best gauge of a person's
            ability to work is the amount of pay received. In deciding whether the person is performing
            SGA, only the pay that has been earned through a person's own effort is counted. If,
            for example, it is necessary for an employer to provide special help for an individual
            to work, the value of such special assistance may be considered a subsidy. As such,
            only those earnings that are based on the individuals own productivity, are used in
            determining total earnings. Additionally, impairment-related work expenses incurred
            by a disabled individual will be deducted from earnings before determining whether
            the SGA level is met.