Simple Harmonic Motion

A particle of mass ' m ' is executing S.H.M. about the origin on $x$-axis with frequency $\sqrt{\frac{\mathrm{ka}}{\pi \mathrm{m}}}$, where ' $k$ ' is a constant and ' $a$ ' is the amplitude of S.H.M. If ' x ' is a displacement of a particle, at time ' $t$ ', potential energy of the particle will be