$[25\%]$Fibonacci heaps a$)(15\%)$Describe the process of sequentially performing the following operations on the Fibonacci heap in Fig. $1$: decrease$-$key $(7,1)$; extract$-$min$()$; min $2593768$Fig$.1$b$)(10\%)$Given a Fibonacci heap with $0,1,2,...,$n keys $($n $=1),$consisting of one vertical chain with marked nodes. How many marked nodes will the resulting tree have after deleting the node with key n$?$Justify your answer.