74. Unless otherwise provided in the articles, when a corporation issues two classes of shares, and there is attached to each such class a right to exchange a share of that class for a share of the other class, if that right is exercised in respect of a share, the amount of issued and paid-up share capital attributable to a share of either class is the aggregate of the issued and paid-up share capital of both classes divided by the number of issued shares of both classes immediately before the exchange.