v₀ = initial velocity of the race car = 21.1 meter/second
v = final velocity of the race car = 57.2 meter/second
t = time for which the race car accelerates = 2.345 second
a = acceleration of the race car
acceleration of the race car is given using kinematics equation as
a = (v - v₀)/t
inserting the values
a = (57.2 - 21.2)/2.345
a = 36/2.345
a = 15.4 meter/second²