An object moves at a constant speed of $10\,\text{m s}^{-1}$ for $20\,\text{s}$. Over the following $10\,\text{s}$, it accelerates uniformly until its speed reaches $20\,\text{m s}^{-1}$. What is the total distance covered by the object in the $30\,\text{s}$?
- A$300\,\text{m}$
- B$350\,\text{m}$
- C$400\,\text{m}$
- D$450\,\text{m}$