You plan to implement a collaboration platform for a company. All 1,000 employees currently use Excel 2010. You have the

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You plan to implement a collaboration platform for a company. All 1,000 employees currently use Excel 2010.
You have the following requirements:
-All employees must be able to co-author Excel workbooks.
-You must minimize the costs associated with any solution.
You need to recommend a solution.
Which solution should you recommend?

A. Implement SharePoint 2013 with Excel Services.
B. Implement SharePoint 2013 and continue using Excel 2010.
C. Implement SharePoint Online and upgrade clients to Excel 2013.
D. Implement SharePoint 2013 with an Office Web Apps server.