There are 3 step calculations :
1. Cash flow from Sale of Equipment -
Sales price (300000)- WDV as per Income Tax (Nil) + Additional Cost to remove (100000) =200000
So after tax cash flow is 200,000x (1-0.40) =120000
2. Working Capital recovered = 400000 (no tax invlovement)
3. Recurring income for 5th Year for 100000 units
Sale price - 80
Mat. Cost - 65
Contribution =15 x 100000 =1500000
Less : Annual Ind. Cost = 500000
Net Profit = 1000000
Net profit after Tax = 1000000 *(1-.4)=600,000
Put together 1+2+3, the net cash flow is 120,000+400,000+600,000 = 1,120,000
Hope this will help you.