Brian lives 1 block west and 3 blocks south of the southwest corner of Green Park. His office is 3 blocks east and 1 block north of the northeast corner of Green Park. On work days he walks on streets to the southwest corner of the park, then takes a diagonal path through the park to the northeast corner, and then walks on streets to his office. If his route is as short as possible, how many different routes can he take?
12
16
20
24
30
