The assumptions used to calculate annual expenses are those used to calculate the accrued retirement benefit obligation  at the end of the previous year. The expected long-term rate of return on plan assets is developed based on the historical  and projected returns for each asset class, as well as the target asset allocation for the pension portfolio. Projected rates  of return for fixed income securities and equities are developed using a model that factors in long-term government  debt rates, real bond yield trend, inflation and equity premiums, based on a combination of historical experience and  future expectations. The discount rate used to determine the accrued retirement benefit obligation is determined by  reference to the market interest rates of high-quality debt instruments at the measurement date. Weighted average assumptions used to calculate the accrued retirement benefit obligation at the end of each year are  as follows: Of the total expense, $101 million (2011 - $103 million), $2 million (2011 - $4 million), and $(1) million (2011 - $1 million)  was included in operating expenses, general and administration expenses and finance income and expenses, respectively. The defined contribution expense for 2012 was $33 million (2011 - $27 million), of which $27 million is included in cost  of sales (2011 - $20 million) and $6 million in general and administration expenses (2011 - $7 million). Generations 111 The amount of employee future benefits expense recognized in profit is as follows: (Cdn$ in millions)  2012 2011 Defined Non-Pension Defined Non-Pension  Benefit Post- Benefit Post-  Pension Retirement Pension Retirement  Plans  Benefit Plans  Plans  Benefit Plans Current service cost  $ 41 $ 10 $ 33 $ 9 Interest cost  82 19 81 20 Expected return on plan assets  (102) – (100) – Past service cost  36 16 56 9 $ 57 $ 45 $ 70 $ 38 2012 2011 Defined Non-Pension Defined Non-Pension  Benefit Post- Benefit Post-  Pension Retirement Pension Retirement  Plans  Benefit Plans  Plans  Benefit Plans Discount rate  3.90% 3.90% 4.41% 4.43% Inflation rate  2.00% 2.00% 2.25% 2.25% Assumed long-term rate of return on assets  6.75% – 6.75% – Rate of increase in future compensation 3.25% 3.25% 3.50% 3.50% Initial medical trend rate  – 7.50% – 7.50% Ultimate medical trend rate  – 5% – 5% Years to reach ultimate medical trend rate  – 6 – 6 Dental trend rates  – 4% – 4% c) Significant Assumptions d) Employee Future Benefits Expense