I have posted this question previously and one of experts gave a completely irrelevant answer! PLEASE let the actual expert to answer this question.

1) HP's class IV and V river guides take the most risks and they deserve an end of season 10% bonus for every class IV or V trip they guided. We need to know the projected amounts of these awards. Create a query that lists GuideFirst, GuideLast, and a new field called ClassBonus. The ClassBonus should be calculated by multiplying the revenue generated by their class IV and V river trips by 10%. Sort in ascending order by the guides' last names and format ClassBonus as currency. Each river guide should only be listed once. Save this as Query14. The Revenue is calculated by Revenue: Ilf([tblCustomer].[Birthdate]10% rate from the revenue by each guide. However, I don't think it is the right amount, which makes the calculation is wrong.. please advice me using IIF function