Rectilinear Kinematics: Integration Using $v\,dv = a\,ds$

A particle's acceleration depends on position: $a = 0.4s\,\mathrm{m/s^2}$, where $s$ is in meters. When $s = 0$, the speed is $v_0 = 3\,\mathrm{m/s}$. Find the speed when $s = 4\,\mathrm{m}$.