20. Repeat Example 4 for the edge cover and minimal corner surveillance when the network is formed by a regular array of north-south and east-west streets of size: (a) 3 streets by 3 streets (b) 4 streets by 4 streets (c) 5 streets by 5 streets 20. Repeat Example 4 for the edge cover and minimal corner surveillance when the network is formed by a regular array of north-south and east-west streets of size: (a) 3 streets by 3 streets (b) 4 streets by 4 streets (c) 5 streets by 5 streets