You and your little brother are rolling toy cars back and forth to each other across the floor. He is sitting at \(x=0\), and you are at \(x=4.0 \mathrm{~m}\). You roll a car toward him, giving it an initial specd of \(2.5 \mathrm{~m} / \mathrm{s}\). It stops just as it reaches him in \(3.0 \mathrm{~s}\).

(a) In what direction is the car's acceleration?

(b) What is the car's average acceleration? -