I did watch the lecture , but i didnt understand this portion to force an NPV = 0, the 4-year annuity factor, AF1-4 = 110,000/40,000 = 2.75 Proof: the NPV calculation would be (2.75 × 40,000) – 110,000 = 0
From tables, the 4-year annuity factor closest to 2.75 is 2.743, corresponding to a discount rate of 17%.
In terms of sensitivity: (17 – 10)/10 = 70% sensitivity
The cost of capital can therefore increase by 70% before the NPV becomes negative.