A car accelerates uniformly from rest at $3\,\text{m/s}^2$ for $4\,\text{s}$. What is its final velocity?

• a)$7\,\text{m/s}$
• b)$12\,\text{m/s}$
• c)$0.75\,\text{m/s}$
• d)$48\,\text{m/s}$