On the Subpart U Overview page you have the option of changing calculation methods.  Please note that you will lose the Subpart U data you have entered if you change calculation method.  If you do need to change calculation method Click change as shown on screen view below:

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Once you have selected a calculation method, you must provide the specific carbonates you have using in your process last year.  Click ADD a Carbonate to open the Carbonate detail page.   Repeat this process for each of the carbonate inputs to your process, each time clicking SAVE.  When you have saved your last carbonate click CANCEL  to return to the Subpart U Overview page. 

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