All amounts actually written off in the accounts of the company during the period between the first day of December, nineteen hundred and fifty, and the date when the bridge first becomes open for public traffic as depreciation in respect of the vessels in the fleet owned by the company:

“Provided that if in respect of any financial year of the company during the aforesaid period the Authority is of the opinion that any amount written off as depreciation as aforesaid is less than the amount which has been or would be allowed by the Commissioner of Inland Revenue by way of ordinary depreciation allowance under the Land and Income Tax Act 1954, the Commission shall, at the request of the authority, fix, for the purposes of this subparagraph, an amount in respect of depreciation for that year which, in the opinion of the Commission, is fair and reasonable in the circumstances and which is not greater than the amount which would, in the opinion of the Commission, be allowed by the Commissioner of Inland Revenue by way of ordinary depreciation allowance under the Land and Income Tax Act 1954:

All amounts actually written off in the accounts of the company during the period between the first day of December, nineteen hundred and fifty, and the date when the bridge first becomes open for public traffic as depreciation in respect of any assets of the company acquired as the result of any additional capital expenditure to which paragraph (b) of this subsection applies:

“Provided that if in respect of any financial year of the company during the aforesaid period the Authority is of the opinion that any amount written off as depreciation as aforesaid is less than the amount which has been or would be allowed by the Commissioner of Inland Revenue by way of depreciation allowance (whether ordinary or special) under the Land and Income Tax Act 1954, the Commission shall, at the request of the authority, fix, for the purposes of this subparagraph, an amount in respect of depreciation for that year which, in the opinion of the Commission, is fair and reasonable in the circumstances and which is not greater than the amount which would, in the opinion of the Commission, be allowed by the Commissioner of Inland Revenue by way of depreciation allowance (whether ordinary or special) under the Land and Income Tax Act 1954.”