Of the following, which are required to be met when a firm wishes to use a portfolio of assets to fund an obligation in a way that also immunizes against interest rate risk? Choose all that are required. The duration of the portfolio of assets being used much be equal to the duration of the obligation The present value of the portfolio of assets being used must be equal to the present value of the obligation The maturity of the portfolio of assets being used must be equal to the maturity of the obligation The default risk characteristics of the portfolio of assets being used must be equal to the default risk characteristics of the obligation