Parametric, Polar and Vector-Valued Functions · Hard problem

A particle has acceleration $\mathbf{a}(t)=\langle 6t,\;2\rangle$ (m/s$^2$) and initial velocity $\mathbf{v}(0)=\langle-3,\;1\rangle$ (m/s). Find its speed, in m/s, at $t=1$.