Land offer

We have some land in section 13-7n-5w (inherited) that we have received a letter wishing to buy the land. There is already a company that leased the mineral rights about 10 years ago. We have received about a royalty check of about $15-20 per year. The company wanting to buy the land has offered $2750 per acre. They know about the mineral rights that are leased but still want to buy the land. I have not idea as to what land is going for in that area. Anybody that could help me in this matter, it would be greatly be appreciated.