Notes to the Financial Statements
Year ended March 31, 2011


j) Tangible capital assets
All tangible capital assets and leasehold improvements having an initial cost of $10,000 or more are recorded at their acquisition cost. Amortization of tangible capital assets is done on a straight-line basis over the estimated useful life of the asset as follows:

Asset class Amortization Period
Buildings 20-30 years
Machinery and equipment 5-20 years
Computer equipment and software 3-10 years
Vehicles 7-10 years
Leasehold improvements Lesser of the remaining term of the lease or useful life of the improvement
Assets under construction Once in service, in accordance with asset class

k) Measurement uncertainty
The preparation of these financial statements requires management to make estimates and assumptions that affect the amounts of assets, liabilities, revenues and expenses reported in the financial statements. At the time of preparation of these statements, management believes the estimates and assumptions to be reasonable. The most significant items where estimates are used are contingent liabilities (include claims and litigation), the liability for employee severance benefits and the useful life of tangible capital assets. Actual results could significantly differ from those estimated. Management's estimates are reviewed periodically and, as adjustments become necessary, they are recorded in the financial statements in the year they become known.