A regulation basketball has a $13cm$ diameter and may be approximated as a thin spherical shell.

How long will it take a basketball starting from rest to roll without slipping $2\mathrm{.}9m$ down an incline that makes an angle of $64\mathrm{.}8$ with the horizontal? The acceleration of gravity is $9\mathrm{.}81\frac{m}{s^2}.$

Answer in units of $s.$