Pursuant to policies approved by the board of directors, differential interest rates may be established for loans based on a variety of factors that may include type, purpose, amount, quality, funding or operating costs, or similar factors or combinations of factors. Differential interest rate programs should achieve equitable rate treatment within categories of borrowers. In the adoption of differential interest rate programs, institutions may consider, among other things, the effect that such interest rate structures will have on the achievement of objectives relating to the special credit needs of young, beginning or small farmers.