Offer to sell mineral rights

I have been considering selling a portion of my mineral acreage (120 acres) in Beckham county. Sections 27 & 28 Township 11N-22W.

A price of $3,200 per acre has been offered for 10 acres in section (28) and 15 acres in section (27). "I don't know what a fair offer would be." Any information that may be available would be helpful in my making a decision to sell a portion of my mineral rights.

Thank you,