A Train Starts from Rest and Accelerates Uniformly Until It $24 \mathrm {~m} / \mathrm { s }$

A train starts from rest and accelerates uniformly until it has traveled 2.1 km and acquired a forward velocity of $24 \mathrm {~m} / \mathrm { s }$ The train then moves at a constant velocity of $24 \mathrm {~m} / \mathrm { s }$ for 400 s.The train then slows down uniformly at 0.065 m/s² until it is brought to a halt.The distance traveled by the train while slowing down is closest to

A) 4.4 km.
B) 4.2 km.
C) 4.0 km.
D) 3.8 km.
E) 3.6 km.