Solve both equations

$2-1$ A rigid beam is supported by pin at $\backslash ($ A $\backslash )$ and cable $\backslash ($ B D $\backslash )$ and $\backslash ($ E C $\backslash )$ as shown. If the force $\backslash ($ P $\backslash )$ causes the end $\backslash ($ C $\backslash )$ of the beam move downward $10$ mm $,$ determine the normal strain in the cable $\backslash ($ B D $\backslash )$ and $\backslash ($ E C $\backslash ).$

$2-3$ The rectangular steel plate is deformed as shown. Determine average shear strain occurred in the plate and the normal strain along the line $\backslash ($ A C $\backslash )$ and $\backslash ($ A B $\backslash ).$