Need to define benefit rates based on coverage and age of employee and dependents

Summary

Need to define benefit rates based on coverage and age of employee and dependents

Content

We have a medical benefit plan where employee selects the coverage amount option and adds dependents. Based on the coverage amount and age of dependent benefit rates should be summed up/ For e.g. let say employee selects coverage amount as 150000 and adds 2 dependents. Age of dependents is <20 and between 20-25. Rate for <20 = 800 and for 21-25 = 1000. Now total of 1800 should be deducted. Is there any mechanism to achieve this.