Whenever an association organized hereunder with preferred stock shall purchase any stock or any property, or any interest in any property, it may discharge the obligations so incurred, wholly or in part, by exchanging for the acquired interest shares of its preferred capital stock to an amount which at par value would equal the fair market value of the stock, property or interest so purchased, as determined by the board of directors. In that case the transfer to the association of the stock, property or interest purchased shall be equivalent to payment in cash for the shares of stock issued.