A fiduciary institution, alone or with one or more cofiduciaries, acting as a fiduciary for fiduciary purposes with the consent of any cofiduciaries, may invest and reinvest funds held in a fiduciary capacity, exercising the care of a prudent investor, in the shares of stock of a mutual trust investment company unless a will, trust indenture, or other instrument under which the fiduciary is acting prohibits that investment.