Bottom rails = ~65 - 70 mm.
Top rails and stiles = ~50 - 55 mm.
Just suggestions. I'm assuming there isn't going to be a middle rail, although there could be if you wanted one. There are all sorts of possibilities but, visually, the bottom rails of doors, particularly doors that go to the floor, or near to the floor look better balanced with the bottom rail wider than the top rail and the stiles. You can even use a formula where the bottom rail is wider than the stiles, which are themselves wider than the top rail. In truth, I prefer the bottom rail of all cabinet type doors wider than the stiles and top rails, even if the bottom rail is at eye level and above. Slainte.
PS. I presume you meant the cabinet height is 850 mm, not 85 mm?