Hi,
Just wanted to point out that in addition to what's explained in the SG, one of the ABRs in Area 1 will be actually installing the route to 150.1.8.0/24 as E2.
Since there's a GRE Tunnel between R2 and R5 in Area 0, R5 will translate LSA type 7 into LSA type 5 and advertise it to R2, which in turn will prefer E2 via Area 0 to N2 via Area 1:
R2#show ip route | include 150.1.8.0
O E2 150.1.8.0/24 [110/20] via 141.1.0.8, 00:49:05, FastEthernet0/0
R2#
R2#show ip ospf database external 150.1.8.0
OSPF Router with ID (150.1.2.2) (Process ID 1)
Type-5 AS External Link States
Routing Bit Set on this LSA
LS age: 946
Options: (No TOS-capability, DC)
LS Type: AS External Link
Link State ID: 150.1.8.0 (External Network Number )
Advertising Router: 150.1.5.5
LS Seq Number: 80000002
Checksum: 0xD8EE
Length: 36
Network Mask: /24
Metric Type: 2 (Larger than any link state path)
TOS: 0
Metric: 20
Forward Address: 141.1.255.8
External Route Tag: 0
R2#
Cheers.