Which set of coordinates most accurately locates the boundary between the Jurassic shales and mudstones and the Cretaceous shales and sandstones?

a. Location 1: 39.701200 degree, -105.201430 degree
b. Location 2: 39.701072 degree, -105.201621 degree
c. Location 3: 39.700935 degree, -105.201790 degree
d. Location 4: 39.700575 degree, -105.202275 degree