6 NORTHERN COLLEGE OF APPLIED ARTS AND TECHNOLOGY Notes to Financial Statements Years ended March 31, 2013 and March 31, 2012 1. Significant accounting policies (continued): (b) Revenue recognition (continued): Contributions received for endowment are reported as an increase in the endowment fund balance. Interest inco me earned on the resources of this endowment fund is reported in the restrict ed fund. Unrestricted investment income is recognized as revenue when earned. Tuition fees are recognized as rev enue based on the number of teaching days within the period. (c) Inv e stments: Portfolio investments are recorded at market value. Sinking-fund investment was recorded at amortized cost. (d) Capital as s e ts : Capital asset purchases are recorded at cost. Contributed capital assets are recorded at fair value at the date of contribution when the fair value is reasonably determinable. Otherwise, contributed capital assets are re corded at a nominal value. Repairs and maintenance costs are charged to expenditu res. Betterments, which extend the estimated life of a capital asset, are c apitalized. When a capital asset no longer contributes to the College’s ability to provide services, it is written down to its residual value. Amortization of capital assets is recorded on the straight-line basis over the following periods: Buildings 40 years Site improvements and parking lots 20 years Leasehold improvements over the term of the lease Furniture and equipment 5 years