How to use Ajax to do a database search based on Column and Row values?

Have an MVC app, and a table with data like this:

dbo.ParameterTable

MainThrust   AST1  AST2   AST3     AST4  AST5
100           2      2      2      2     2
200           3.4    3.7    4.1    4.4   5.2
500           5      5.6    6.5    7.4   8
1000          8      9.4    11.2   14.4  16
5000         12      14.1    18    20    25

Textbox 1 (AST Value)

Textbox 2 (Mainthrust value)

Textbox 3 resulting value

So if the user enters 2 in textbox 1, this means its value is AST2;  then the user enters 500 in Mainthrust, now we have the x and y for this table.  How in the view can you use Ajax to send these 2 values into the controller function?    And what would the logic be for LINQ to get the value?  

function (ValX, ValY)

var resultvalue =  (from  TempVal in db.ParameterTable

    where TempVal.Mainthrust == ValX

    select new

        {  AST1 }.ToList());

back in the view

 ajax   

      success(data)

var x = JSON.Parse(data);

$('#MyTextbox3').val(x[0].AST1);

Ajax in the View does the call.  I already have the trap for catching both textboxes in the View,

$('#Mainthrust').change(function () {

when the user adds a value and clicks away from that textbox it comes into the javascript and I have made the code to get the value in the 2 textboxes.

But now?  sending these 2 values by ajax and expecting it to return the value within the table there?  the column AST2 and Mainthrust value = 200 must return the lookup value of "3.7"

Seems like a useful design pattern, but I have not done much with ajax, thanks for any ideas