return value from the intersection of a particular row and column in a table

Hello,

I have the attached mathcad with the inputs: "a", "b" and "Table". "a" should be looking in the first row of "Table" to find a match, vector "b" should be looking in the first column of "Table" to find a match for each value of the vector. The final result should return the result from the intersection of the column and line previously identified to get the result from "Table". 

Thank you,

Otilia