(a)
The shaded area which is equal to \(\frac{1 }{ 2} \times 4 \times 6 = 12 \;m\) represents the distance travelled by the car in the first \(4\) \(s\).
(b)
The part of the graph in red colour between time \(6\) s to \(10\) \(s\) represents uniform motion of the car.
The rate at which an object covers a certain distance is commonly known as speed.
The rate at which an object changes position in a certain direction is called velocity.
Read More: Difference Between Speed and Velocity