C# and MS access SQL - how do I create a query that sums 2 columns of one table with one column from another table

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C#

SQL

MS-Access

I am a beginner developing a WinForms application in Visual Studio 2015 using C# .Net connecting to a MS Access 2016 database. What I am trying to do is to add (SUM, I guess) the values of three columns: two from the same table and one column from another. The table structure is as follows:

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Table Products: Product, Cost1, Cost2

Table OtherCosts: Cost3

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I need a query that returns the following:

Product, AllCosts

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Thank you very much for your time and help. I really appreciate it.

What I have tried:

SELECT Product
FROM tbl_products

UNION SELECT Price1 AS Price
FROM tbl_products

UNION SELECT Price2 AS Price
FROM tbl_products

UNION SELECT Proce3 AS Price
FROM tbl_othercosts;