The container with water in it has a mass of $30 \mathrm{~kg}$. Block $B$ has a density of $8500 \mathrm{~kg} / \mathrm{m}^{3}$ and a mass of $15 \mathrm{~kg}$. If springs $C$ and $D$ have an unstretched length of $200 \mathrm{~mm}$ and $300 \mathrm{~mm}$, respectively, determine the length of each spring when the block is submerged in the water.