The athlete shown in Figure $\mathrm{P} 4.25$ rotates a $1.00-\mathrm{kg}$ discus along a circular path of radius $1.06 \mathrm{~m}$. The maximum speed of the discus is $20.0 \mathrm{~m} / \mathrm{s}$. Determine the magnitude of the maximum radial acceleration of the discus.