Answer
$$-0.710 \mathrm{\ J} / \mathrm{K}
$$
Work Step by Step
The change in entropy for block $L$ is
$$
\Delta S_{L}=m c \ln \left(\frac{T_{f}}{T_{i L}}\right)=(0.101 \mathrm{kg})(386 \mathrm{J} / \mathrm{kg} \cdot \mathrm{K}) \ln \left(\frac{300.0 \mathrm{K}}{305.5 \mathrm{K}}\right)=-0.710 \mathrm{J} / \mathrm{K}
$$
