Answer
$$+1.72 \mathrm{\ J} / \mathrm{K}
$$
Work Step by Step
The change in entropy is
$$
\begin{aligned} \Delta S &=\Delta S_{1}+\Delta S_{2}=m_{1} c_{1} \ln \left(\frac{T_{f}}{T_{i, 1}}\right)+m_{2} c_{2} \ln \left(\frac{T_{f}}{T_{i, 2}}\right) \\ &=(50.0 \mathrm{g})(386 \mathrm{J} / \mathrm{kg} \cdot \mathrm{K}) \ln \left(\frac{320 \mathrm{K}}{400 \mathrm{K}}\right)+(100 \mathrm{g})(128 \mathrm{J} / \mathrm{kg} \cdot \mathrm{K}) \ln \left(\frac{320 \mathrm{K}}{200 \mathrm{K}}\right) \\ &=+1.72 \mathrm{\ J} / \mathrm{K} \end{aligned}
$$
