Under U.S. GAAP, which of the following is the requirement for how a companys pension liability should be calculated? a. The pension liability should be calculated using vested benefits and employees current salaries b. The pension liability should be calculated using vested and non-vested benefits and employees current salaries c. The pension liability should be calculated using vested benefits and employees future salaries d. The pension liability should be calculated using vested and non-vested benefits and employees future salaries e. None of the above