Refering to this image:

Users on the 192.168.1.0/24 network must access files located on the Server 1. What route could be configured on router R1 for file requests to reach the server?
The Answer is ip route 0.0.0.0 0.0.0.0 s0/0/0
what I want to know is why is this the answer? How do you figure this out?