Can anyone please tell the solution for the answer to this

Dear student,
(1)No, the car is not moving constant velocity as the ratio of distance and time is not same for all the observations.
(2)The average speed is $\frac{15+28+40+60}{30+30+30+30}$$=\frac{143}{120}=1.191$
hence,average speed is 1.911 Km/min=71.46 km/h
Regards.