Final answer:
The acceleration (or deceleration) of Samantha's car is -4.5 m/s^2.
Step-by-step explanation:
The acceleration (or deceleration) of Samantha's car can be calculated using the formula: acceleration = change in velocity / time taken. Since her car comes to a stop (0 meters per second) from a velocity of 27 meters per second, the change in velocity is -27 m/s (negative because it's a deceleration). The time taken is 6 seconds. So, the acceleration (or deceleration) is:
acceleration = -27 m/s / 6 s = -4.5 m/s^2
So, the correct answer is -4.5 m/s^2.