Additional Exercise 3. On a grid, let A=(0,0),B=(10,12),C=(4,3),D=(6,9), E=(9,7). Find the number of (shortest) grid walks AB that: (a) pass through C (b) do not pass through D (c) pass through C but not D (d) pass through C and E (e) pass through either D or E Additional Exercise 3. On a grid, let A=(0,0),B=(10,12),C=(4,3),D=(6,9), E=(9,7). Find the number of (shortest) grid walks AB that: (a) pass through C (b) do not pass through D (c) pass through C but not D (d) pass through C and E (e) pass through either D or E