Before the issuance of any individual contract on a variable basis, the insurer shall reasonably satisfy itself that the total amounts being applied and proposed to be applied to provide the prospective annuitant with income on a variable basis will not substantially exceed the amount which would be required to purchase the income in a predetermined dollar amount which the annuitant can reasonably expect to receive. In determining the reasonably expectable fixed dollar income, the insurer may consider, alone or in combination, any direct source, such as a pension, annuity, Social Security benefit, or trust fund, as well as any indirect source, such as an asset having a principal amount expressed in fixed dollars and capable of being used to produce a fixed dollar income, as, for example bonds, mortgages or life insurance policies.