Notwithstanding any limitation or prohibition otherwise imposed by any provision of law exclusively relating to banks or savings associations, other than the limitation on the amount of investment by a Federal savings association contained in section 1464(c)(4)(B) of this title, an insured depository institution may invest not more than 10 per centum of paid-in and unimpaired capital and unimpaired surplus in a bank service company. No insured depository institution shall invest more than 5 per centum of its total assets in bank service companies.