Each member of a development credit corporation shall lend funds to the development credit corporation as and when called upon by it to do so to the extent of the member's commitment, but the total amount on loan by any member at any one time shall not exceed the following limit: (1) For banks, trust companies, or insurance companies, three percent of capital and surplus; (2) For mutual savings banks, savings and loan associations, or credit unions, three percent of guaranty and reserve funds; and (3) Comparable limits for other institutions. All loan limits shall be established at the thousand dollars amount nearest to the amount computed on an actual basis. All calls when made by this corporation shall be prorated among the members on the same proportion that the maximum lending commitment of each bears to the aggregate maximum lending commitment of all members.