The graph shows tax payable against taxable income, in thousands of dollars.

- Use the graph to find the tax payable on a taxable income of \($18\ 000\). (1 mark)

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- Use suitable points from the graph to show that the gradient of the section of the graph marked \(A\) is \(\dfrac{7}{15}\). (1 mark)

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- How much of each dollar earned between \($18\ 000\) and \($33\ 000\) is payable in tax? (1 mark)

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- Write an equation that could be used to calculate the tax payable, \(T\), in terms of the taxable income, \(I\), for taxable incomes between \($18\ 000\) and \($33\ 000\). (2 marks)

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