No savings bank shall make an investment pursuant to this act at any time
(a) when the total of all of such investments exceeds, or if the making of such investment would cause such total to exceed 10% of its deposits; or
(b) when the total of all such investments in the revenue bonds of one unit exceeds, or if the making of such investment would cause the total investment in the revenue bonds of any 1 unit to exceed 1% of its deposits; or
(c) when the total of all such investments in revenue bonds of any 1 unit exceeds, or if the making of such investment would cause such total to exceed 5% of the total amount of all revenue bonds of that unit issued and outstanding.