Two cars X and Y move along the same straight road. Car X moves with a steady speed of $6.0\ \text{m s}^{-1}$. Car Y has a steady acceleration of $0.50\ \text{m s}^{-2}$. At the instant shown, car X is ahead of car Y by a distance $d$. Car Y is moving at a speed of $4.0\ \text{m s}^{-1}$. After $20$ seconds, car Y is level with car X. What is the distance $d$?
- A$40\ \text{m}$
- B$60\ \text{m}$
- C$180\ \text{m}$
- D$300\ \text{m}$