A $2\mathrm{.}0-$kg particle undergoes simple harmonic motion according to x $=1\mathrm{.}5$sin$($t$/4+$ $/6)($in SI units$)($a$)$ What is the total mechanical energy of the particle? $($b$)$ What is the shortest time required to move form x $=0\mathrm{.}5$m to x $=-0\mathrm{.}75$m$?$