Create a workflow that adds the values on column A with values on column B and writes them in column C in different ways

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I am new to ui path, i have scenario like Create a workflow that adds the values on column A with values on column B and writes them in column C in different ways,Keeps the excel open and writes the results in real time, row by row so you can see the changes Keeps the excel closed, set the column values in the memory DataTable and adds all the table to the excel file at once, in the end and Calculates the SUM by using excel formulas

Please help to resolve above scenario.