Jose is correct, IOS still uses the path selection as defined in RFC 1583 (for backwards-compatibility):
Path-type
There are four possible types of paths used to route traffic to
the destination, listed here in order of preference: intra-area,
inter-area, type 1 external or type 2 external. Intra-area
paths indicate destinations belonging to one of the router's
attached areas. Inter-area paths are paths to destinations in
other OSPF areas. These are discovered through the examination
of received summary link advertisements. AS external paths are
paths to destinations external to the AS. These are detected
through the examination of received AS external link
advertisements.
This has been changed in RFC 2328, which is the default in NX-OS:
Intra-area paths using non-backbone areas are always the most preferred
The other paths, intra-area backbone paths and inter-area paths, are of equal preference
You can change the behavior with the [no] compatible rfc... command.
The order of preference takes priority over path cost and even administrative distance.
If the link between R2 and R4 would belong to area 1, the least cost path (via R4) would be prefered.
Hope that helps
Rolf
P.S.: What exam is that question from?
