Answer
$t=5.66s$
Work Step by Step
We can determine the required time as follows:
$a_{max}=\frac{\mu_s N}{m}=\mu_s g$
We plug in the known values to obtain:
$a_{max}=0.3(9.81)=2.943m/s^2$
Now $v=at$
$\implies t=\frac{v}{a}$
$\implies t=\frac{50/3\space m/s}{2.943m/s^2}$
This simplifies to:
$t=5.66s$