tax working in investment apprisal

Dear Sir,
i found some questions in investment appraisal not included separate working for tax, whereas some other questions. what is the criteria to have separate working for tax?

see below example.

A major retail company which sells its ‘own brand’ products is deciding whether to open new retail outlets in a rapidly expanding overseas market. Past experience from entering other overseas markets has shown that acceptance of the brand can depend on a number of factors and that sales in the first four years are a good indicator of the potential of the market for the future.
Year 1 sales will depend on how readily the brand is accepted. A consultancy firm, with experience of the overseas market, was employed at a cost of $0.5m to provide detailed information on the market and an estimate of the likelihood of the brand being accepted. The consultancy firm estimated that there is a 50% chance that the brand will be well received and sales in year 1 will be $450m, there is a 20% chance that the brand will be very well received and sales in year 1 will be $600m, and there is a 30% chance that the brand will not be well received and sales in year 1 will be $300m. Sales are then expected to increase by $100m each year, irrespective of sales in the first year.
An investment of $600m is required to develop and fit out the retail outlets. The costs will be depreciated on a straight line basis over the four year period. The development and fit out costs will be eligible for tax depreciation. It is expected that the retail outlets will have a residual value of $400m at the end of four years. The residual value will be treated for tax purposes as a balancing adjustment. There will also be a requirement for $60m of working capital.
The average contribution to sales ratio is expected to be 60%. Fixed costs relating to the retail outlets, including depreciation, are expected to be $150m per annum and will remain the same for the four year period. It is also anticipated that a further $50m will be spent in each of the four years on marketing the brand.
The company’s financial director has provided the following taxation information:
• Tax depreciation: 25% reducing balance per annum.
• Taxation rate: 30% of taxable profits. Half of the tax is payable in the year in which it arises, the balance is paid in the following year.
• Any taxable losses resulting from this investment can be set against profits made by the company’s other business activities.
The company uses a post-tax cost of capital of 8% per annum to evaluate projects of this type. Ignore inflation.

Advise the directors of the company whether they should go ahead with the investment from a financial perspective.
how to work it out without seperate working for taxation and just use captial and operatign cash flow working.
Ahmed