Setup complex rate based on employee contribution

Summary

Need to setup a 2 tier rate for employer match based on employee contribution

Content

I have a requirement to create a 2 tier employer match rate based on employee contribution.  The employer will match 100% of the employees 1st 3% contribution & 50% of the employees 2nd 2% contribution.

Example:

Person A contributes 3% of earnings, the employer will contribute 3% of earnings

Person B contributes 4% of earnings, the employer will match 3.5% of earnings

Person C contributes 5% of earnings, the employer will match 4% of earnings

How can I achieve this requirement?  Do I need to create 2 flat rates in benefits, 1 with 100% and another with 50%?  I tried using a Rate Value Calculation fast formula but don't see how to reference the employees election.