(1)In calculating, for the purposes of sections 275, 276 and 277, the number of companies of which a person may be a Director, the following companies shall be excluded, namely:-(a)a private company which is neither a subsidiary nor a holding company of a public company;(b)an unlimited company;(c)an association not carrying on business for profit or which prohibits the payment of a dividend;(d)a company in which such person is only an alternate Director, that is to say, a Director who is only qualified to act as such during the absence or incapacity of some other Director.