Need help to choose the right function.

Hi,

Can someone please advise how to get around this. I have two inputs as shown in the attached photo, in red and green. What kind of function that would return a value i.e. orifice size, from the very first left column based on these two inputs?

in the example below the function should start by looking for a value of 100 in the first row of the array which is in this example (3rd column in the array here) and then search in that column to find 9, then returns 12.7 from the first column

Thanks