When to use before-tax weighted avg cost of capital or after-tax weighted avg

We always use the after-tax WACC unless specifically told to do otherwise. It would be nonsense to use the pre-tax WACC unless the question told you to (which is unlikely).

Thank you. I see from the answer now that because the question says ignore taxation this is why we use the before tax weighted cost "Since taxation and capital allowances are to be ignored, and where relevant all information relating to project 2 has already been adjusted to include future inflation, the correct discount rate to use here is the nominal before-tax weighted average cost of capital of 12%."

You are welcome :-)