At an outdoor market, a bunch of bananas is set on a spring scale to measure the weight. The spring set the full bunch of bananas into vertical oscillatory motion. The motion is harmonic with an amplitude of 0.15 m. The spring of the scale has a force constant k = 332 n/m. It is observed that the maximum speed of the banans is 1.56m/s. What is the mass of the banana bunch in units of kg?