How can we sum transaction amount of salesrep to assign it to manager

Hi all,

I have a requirement to calculate the incentive for manager as per his rate table based on his achievement which is measured as;

                                                  Target                         Transaction

Salesrep1                                  100000                         90000

Salesrep2                                  120000                        110000

Salesrep3                                  100000                        100000       

Manager                                   320000                         300000

As per their target and Transaction amount Manager and Sales rep have separate rate tables. so how can we calculate manager achievement on the basis of salesrep target and transaction amount?