Commission Formula w/Accelerators based on Quota Range & Term Length? attatched worksheet

I'm in need of a formula for the following:

Up to 100% of annual quota - they get 8.5% (BUT - any deal less than twelve months must also be calculated based on term length as well)

greater than 100 of less than 133% of quota - 12% commission rate - again, anything less than 12 months on a deal should calculate on the appropriate rate PLUS the term length

greater than 133% of quota - 15% (again, anything less than 12 months on a deal should calculate on the appropriate rate PLUS the term length)

Seems a bit too complicated for this Excel brain - any help out there? Much appreciated. Thank you!