369.699.  Limits on investment. — 1.  A savings bank may not invest more than forty percent of its total assets in commercial loans.  A commercial loan is a loan for business, commercial, corporate or agricultural purposes.

  2.  A savings bank shall maintain at least fifteen percent of its assets in assets and investments taken from the following categories:

  (1)  First and second lien residential mortgage loans or foreclosed residential mortgage loans;

  (2)  Home improvement loans;

  (3)  Interim residential construction loans; and

  (4)  Mortgage-backed securities.