Google Sheets Formula

We are trying to make a dynamic calculation on our "Bid Sheet". The Bid Sheet should be where the calculations final output will be. The "Products/Services" and "Rates" sheets are for reference for the calculations. We want the drop down menu “Item" and “Model" on the Bid Sheet to select the appropriate item on the “Products/Services" sheet and “Rates” sheet and fill in the price each and labor hours for the appropriate drop down item. In the examples given (A4 through F4) we were only able to hard code the calculations. We need them to be dynamic so that when any combination of “item” and “model” is selected the correct price and labor hours from the Products/Services and Rates sheets show for the selections. We plan to manage the labor hours on the Rates sheet so if we need to change the labor rate calculation, we want to do so by only changing the value on the “Rates” sheet. We plan to manage the Products/Services costs on the "Products/Services” sheet, we want to do so by only changing the value on the "Products/Services” sheet. If you do not understand my explanation, please let me know, I would be happy to clarify.