Question 984983
<pre>

upstream       r-c       u        d
downstrm       r+c       b        d


upstream       r-c       u        d=(r-c)*u
downstrm       r+c       b        d=(r+c)*b

</pre>


{{{(r-c)*u=(r+c)*b}}}


Solve for c.


{{{system(r=37,u=43/60,b=31/60)}}}
Evaluate c.