sharpest lens for shooting small/large artwork

[Monetbeck00]

What is the sharpest prime autofocus Canon lens for shooting artwork ranging in size from 8x10" to 40x60"?

UPDATED w info requested in replies (thank you, guys)...

I need super-sharp photos of my paintings, which range in size from 8x10" to 40x40". I am shooting with my EOS RP. I can shoot by available light outdoors (not in direct sunlight) or with my Elinchrome strobes. Indoors, I have about 10- 15' to move back from the artwork. Someone recommended the Canon 180mm EF Macro (Ken Rockwell says it's the sharpest Canon macro lens). My budget is up to $600, and I don't mind a used or refurbished lens. I do need autofocus due to lousy eyes. I am also wondering if a macro lens will work for large artwork. 

Thanks for your feedback!

[Waddizzle]

I think your best approach to capture high resolution images of the artwork is going to be capturing multiple smaller images and stitching them together in post processing to create a final image that would have much higher resolution than a single photo of the entire piece. 

This approach may blow your budget, but I feel it is much better than a single photograph that may look like a snapshot.