What is the net present value of annual maintenance cost for a delivery vehicle?

[waptrick]

The estimated annual maintenance cost associated with the delivery vehicle amounts to R14 000 for the first year that the vehicle will be used (payable at the end of the year). The annual maintenance cost for the subsequent two years will increase by 4% per year as a result of wear and tear. During the last two years that the vehicle is used the annual maintenance cost will further increase by 9% per year. Calculate the net present value of the maintenance cost now. The cost of capital is 11% p.a

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The answer is 46 304.87. But I have no idea how to get there

 

[MarkFL]

Net Present Value is given by:

\(\displaystyle \text{NPV}=\sum_{t=1}^{n}\frac{R_t}{(1+r)^t}\)

In this formula, $r$ represents the discount rate, however, we are only given cost of capital. Do you have a means of getting the discount rate from the cost of capital?