Starting from the origin at time $t=0$, with initial velocity $5 \hat{j} \mathrm{~ms}^{-1}$, a particle moves in the $x-y$ plane with a constant acceleration of $(10 \hat{i}+4 \hat{j}) \mathrm{ms}^{-2}$. At time t , its coordinates are $\left(20 \mathrm{~m}, \mathrm{y}_0 \mathrm{~m}\right)$. The values of $t$ and $y_0$ are, respectively