Getting duplicated from two sheets and outputting the difference of their associated costs

Hello,

I have an excel file with 2 spreadsheets. Each has two columns. Column A has a name and Column B is a list of costs associated with each name.
I need to write a macro which finds all duplicates in Column A of both sheets and outputs that onto a third sheet. Then I need the macro to also subtract Sheet2's cost from Sheet1 and output that as well onto the third sheet. It should get the difference for each name. Then rearrange the data alphabetically.

Example
Sheet1 Sheet2 Sheet3
Jane 1 David 5 Alice 1
Alice 2 Jane 3 David 5
Mark 4 Alice 1 Jane -2
David 10 John 4


Here is my code so far:

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Any help is appreciated!
Thanks so much!