Selling mineral interests

I just posted a question on another discussion that probably should have been posted here, so I will post this again.

We received an offer from Anthem Inc to purchase 2 of our mineral interests in Martin County. The offer was much higher than previous offers. I am wondering if there have been others of the higher offers and how does one decide to sell or continue the royalties?

Need legal descriptions to give a valid answer.

I need to add to the description that it is all of Section 4. All of Section Four (4), Block 37, Township 1 South, T&P Rwy. Co./J.S. Day Survey, Abstract 642, Martin County, Texas.

I have mineral rights in Martin County, Labor 1, League 259, Borden County School Land. I have received several offers. There are two wells presently producing from the Sprayberry. What would be a reasonable offer?