Subject to section 519, if the company is a company limited both by shares and by guarantee, neither of sections 516 and 517 applies but the member need not contribute more than the aggregate of the following:
(a) the amount (if any) unpaid on shares in respect of which the member is liable as a present or past member;
(b) the amount that the member has undertaken to contribute to the company's property if the company is wound up.