Problem $4(10$ points$)$: Show the start and the finish timestamps determined by DFS for the graph below, and then based on the timestamps provide a topological sort of the nodes of the graph. Your starting node is $a.$ If there are nodes unreachable, then you choose a new starting node to start DFS again, until every node has been reached. When there are multiple candidate nodes to choose as your new starting node or when there are multiple candidate nodes to choose as your next node to visit in DFS$,$ pick the node in the alphabetical order of the candidate nodes $($i$.$e$.,$ the same rule as in Problem $2).$

Note: $($i$)$ Please use $1$ as the start timestamp for $a$; $($ii$)$ Please explicitly show the two timestamps for each node, and then separately point out the topological sort.