How to analyze multiple conditions in a row, return an answer in the same row, new column

I'm trying to analyze multiple cells in any row of data, have a look-up of either a value based on a term in the same row, and return a value (either a flat amount, or sometimes needing a computation) in the same row in a new column.

For example, each person has multiple tasks to perform, and can be paid a commission based on the task definition, but each defined task pays a different commission.

The logic in this example is in column D, with results placed in column E.

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My challenge is there are up to 40 different people with multiple commission rates based on up to a half dozen tasks, so each line can yield a completely different commission computation. I'm pretty good at using nested if statements, but I suspect something this complex will need more knowledge that I currently have! I don't know how to attack this as there seems to be far too many variables then simple if statements or something similar can compute. I'm looking for anyone who can point me in the right direction. If i can understand how to build something for just one person, I need to be able to do the same adding multiple people and multiple computational variable.

Thanks in advance for any assistance.

Bruce