Explanation: Cost before tax = \(Tk~80\). Total price including tax = \(Tk~96\). Tax amount = \(96 - 80 = Tk~16\). Tax Rate = \((\text{Tax amount} / \text{Cost before tax}) \times 100\%\). Tax Rate = \((16 / 80) \times 100\% = (1/5) \times 100\% = 20\%\).