1. Calculate the ci for several races.
2. Populate a table with your results. Use the ci for the rows and odds for the columns. The body of the table will be the roi for each combination of ci and odds. I guarantee you that you will be amazed at the results. It should look something like this (several columns omitted):

Return on Investment

****odds range***
****1-2*****8-9
1**********-14.32%
2*-13.70%**-16.89%
3*-14.24%**-19.69%
4*-13.96%**-19.88%
5*-13.39%**-19.57%
6*-13.19%**-25.16%
7*-12.65%**-18.55%
8*-13.39%**-27.85%
9*-10.32%**-37.51%

ci x 100