I agree with Welder and also I add that I was not able to find an easy way out to this one! Probably there is an easy way to solve it but I didn't find it.
What I tried was to use a "Brute Force" approach...
Basically, I tried values of
I also cheated because I used Excel to do it for me!!!
As you can see, I built a table in Excel trying to get the required value:
In the first column are listed values of
The best result was reached for:
Well, I hope it helps...