Answer
$E=0.436J$
Work Step by Step
For an undamped simple harmonic oscillator, energy is conserved. This means that the total energy is either elastic potential or kinetic. In this case, elastic potential energy can be expressed as $$U=\frac{1}{2}kA^2$$ Substituting known values of $k=13.3N/m$ and $A=0.256m$ yields a total mechanical energy of $$U=\frac{1}{2}(13.3N/m)(0.256m)^2=0.436J$$
