OSPF areas have been planed like in picture Scheme_1.jpg. ASBR 1 and ASBR 2 advertises default route.
Problem: sites 52, 53, 56, 58 uses default route to ASBR2, inspite of fact that metric to ASBR1 is lower.
By OSPF theory between ASBRs router choose ASBR in the same area. If all ASBRs are situated in another areas router choose ASBR by metric.
Replanning areas (Scheme_2.jpg). In this network scheme routers 52, 53, 56, 58 chooses ASBR by metrics (it will be ASBR 1). All routers in area 2 choose ASBR 2.