(i)in the case of a company other than a company whose accounts are subject to audit by an auditor appointed by the Comptroller and Auditor-General of India, be filled by the Board of Directors within thirty days, but if such casual vacancy is as a result of the resignation of an auditor, such appointment shall also be approved by the company at a general meeting convened within three months of the recommendation of the Board and he shall hold the office till the conclusion of the next annual general meeting;