$(4)$ Suppose we construct a Splay tree from scratch by using the following eight steps. What is the inorder traversal of the Splay tree? $(5\%)$

Stepl: insert $40$

Step$2$: insert $80$

Step$3$: insert $70$

Step$4$: insert $50$

Step$5$: insert $90$

Step$6$: delete $70$

Step$7$: insert $70$

Step$8$: delete $80$