Need help regarding design of Rate race mixer

Hi friend
I want to design Rate race mixer in ADS.
The ring is 1.5lambada in circumference.
but i don't know how to use that Mcurve bend.
How to set the radius & angle to get perimeter of 0.25*lambada(lambada by 4) & 0.75*lambada?
I do not find in ADS help.
waiting for your replies
Abhishekabs