A horizontal spring attached to a wall has a force constant of k $=770$ N$/$m$.$ A block of mass m $=1\mathrm{.}20$ kg is attached to the spring and rests on a horizontal, frictionless surface as in the figure below. A block labeled m is attached to the right end of a spring labeled k$,$ and the left end of the spring is attached to a wall. Three positions of the block are shown. From left to right, the positions are labeled x $=0,$ x $=$ xi$/2,$ and x $=$ xi$.($a$)$ The block is pulled to a position xi $=5\mathrm{.}00$ cm from equilibrium and released. Find the elastic potential energy stored in the spring when the block is $5\mathrm{.}00$ cm from equilibrium and when the block passes through equilibrium. x $($cm$)$ Elastic Potential Energy $($J$)($b$)$ Find the speed of the block as it passes through the equilibrium point. m$/$s $($c$)$ What is the speed of the block when it is at a position xi$/2=2\mathrm{.}5$ cm$?$ m$/$s $($d$)$ Why isn't the answer to part $($c$)$ half the answer to part $($b$)$