The plan administrator shall value all benefits as of the valuation date by—

(a) Using the mortality assumptions prescribed by § 4044.53 and the interest assumptions prescribed in appendix B to this part;

(b) Using interpolation methods, where necessary, at least as accurate as linear interpolation;

(c) Using valuation formulas that accord with generally accepted actuarial principles and practices; and

(d) Adjusting the values to reflect loading expenses in accordance with appendix C to this part.