for part (a), i inflated all the cash flows, calculated tax charge, capital allowances and working capital requirements (based on inflated sales). I discounted them all at the monetary cost of capital, t0 obtain a +ve NPV of USD 4,000,000.
For part (b) i used the revenue and cost AS STATED in the question, calculated all other cashflows (tax and all others) and discounted them at a REAL cost of capital of 7%….again i obtained a +ve NPV