If \( 80 \, \text{g} \) of copper sulphate \( \mathrm{CuSO_4 \cdot 5H_2O} \) is dissolved in deionized water to make \( 5 \, \text{L} \) of sodium. The concentration of the copper sulphate solution is \( x \times 10^{-3} \, \text{mol L}^{-1} \). The value of \( x \) is:
