Colorado Lease Offer

Looking for some guidance..

Township 8 North, Range 66 West, 6th PM, Section 20.

Offered $750 per acre at 20% royalty. Declined and then offered $1000 (18.75%) or $1250 (16.67%).

What is a good offer for my area at the moment? Is a 5 year lease with a 3 year option standard?