$(7$ pts$.)$ Problem $3$ The dam is $200$ m long with a $2-$m$-$thick permeable sand layers, as shown in the figure. The hydraulic conductivity of the sand layer $1$ is $2\mathrm{.}6\frac{m}{?}$ day, and for the sand layer $2$ is $1\mathrm{.}2\frac{m}{?}$ day. Both sand layers have the same thickness. If the water elevation in the standpipe is $150$ m $,$ What is the water elevation behind the dam?

b$)$ for the same soil properties What is the water elevation behind the dam?