The condition of the problem is incorrect, so it will not be solved.
Assume that v0=0 , vc=2vb , vd=3vb
a=const and BC=200(m) .
s2=2a(2vb)2−vb2→a=2s23vb2
s1=2avb2−0=2⋅3vb2vb2⋅2s2=3200≈67(m)
s3=2a(3vb)2−(2vb)2=2⋅3vb25vb2⋅2s2=2⋅35⋅2⋅200≈333(m)
s=s1+s2+s3=67+200+333=600(m) . Answer
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