M11-03 (600) If a passenger sitting near the window in a tra

I understand the provided solution but anyway I am curious what am I doing wrong here:

R=40 \frac{km}{h}=\frac{100}{9} \frac{m}{s}

T=3 s

D=75 m

Speed of the oncoming train in meters per second = N
Solution:

(\frac{100}{9}+N)*3=75

\frac{100}{9}+N=25

N=25-\frac{100}{9}

N=LT15\frac{m}{s}=LT54 \frac{km}{h}

So I am picking the B. Where is the bug?