kinetic energy of the block \(=\) (\(P.E\) of commpressed spring)\(+\)work done against friction.

\(\frac{1}{2} \times 2 \times {\left( 4 \right)^2} = \frac{1}{2} \times 10,000{x^2} + 15 \times x\)

\(10,000\)\({x^2}\)\(+30x - 32 = 0\)

\( \Rightarrow \,5000{x^2} + 15x - 16 = 0\)

\(\therefore \,x = \frac{{ - 15 \pm \sqrt {{{\left( {15} \right)}^2} - 4 \times \left( {5000} \right)\left( { - 16} \right)} }}{{2 \times 5000}}\)

\(=0.055m = 5.5 cm.\)