Is it possible to bill Customers based on transactions volumn and rates without having specific cont

Hello Gurus.

My client has a home grown system which collects the transactions or terminal usage data from about seven external systems and bill it through AR . There is a requirement if the current home grown system can be replaced by Oracle Projects

I have following business requirements.

1. There are about seven third party systems which send the usage data ( number of transactions made ) through various types of files.

2. For each customer, there are rate types ( code) and rate in $

3. Rate are based on number of transactions. For example 1-100 transactions, the rate will be $0.10. From 100-300 transactions the rate will be $0.20 etc.