I would like to multiply a cell by a number on a separate sheet; but defined by a drop down

Here is an idea of what I think the excel formula would look like:

=IF(C4=1), THEN multiply A4(Sheet1) by B4(Sheet2)

I have two sheets. A reference sheet (Sheet 2) and a Primary Sheet (Sheet 1). On the reference sheet there is a data table. The top line from C3 to J3 is numbered 1 to 9.

Under neath these numbers are decimal numbers, for example 1.29 in C4.

On Sheet 1 (primary) I have a QTY column, a PRODUCT column, an APPLICATION column and a PRICE column.

In QTY I have 9303. In Application column I have an array that is a drop down that is selectable from 1-9. Depending on what the user selects in this column, I want it to reference the correct cell on the Reference sheet (for example C4=1.29) and multiply that by the QTY in A4.

Can anyone help with the best way to do this via excel?

I have tried nesting IF before SUMPRODUCT. SUMPRODUCT is working to accurately multiply A4(Sheet1) by C4(Sheet2) and the value it returns is correct.

I would like to see QTY multiplyed by the value that is referenced beneath the number of applications.

So if The user selects 2 Applications, the number 2 value that would be in C5 is multiplyed by QTY in the next field.