A mutual savings bank may invest not to exceed twenty percent of its funds in the following:

(1) Bankers' acceptances, and bills of exchange made eligible by law for rediscount with federal reserve banks, provided the same are accepted by a bank or trust company which is a member of the federal reserve system and which has a capital and surplus of not less than two million dollars, or commercial paper which is a prudent investment.

(2) Bills of exchange drawn by the seller on the purchaser of goods and accepted by such purchaser, of the kind made eligible by law for rediscount with federal reserve banks, provided the same are indorsed by a bank or trust company which is a member of the federal reserve system and which has a capital and surplus of not less than two million dollars.

The aggregate amount of the liability of any bank or trust company to any mutual savings bank, whether as principal or indorser, for acceptances held by such savings bank and deposits made with it, shall not exceed twenty-five percent of the paid up capital and surplus of such bank or trust company, and not more than five percent of the funds of any mutual savings bank shall be invested in the acceptances of or deposited with a bank or trust company of which a trustee of such mutual savings bank is a director.