Suppose a computing system uses a virtual memory system. Virtual addresses are $64$ bits and physical pages

are $32$ bits.

$($a$)$ A running process attempts to access memory. The page table entry has the following information:

What action is taken by the virtual memory hardware?

$($b$)$ The process then attempts another memory access. The page table entry has the following information:

What action is taken by the virtual memory hardware?

$($c$)$ The process then attempts another memory access. The page table entry has the following information:

What action is taken by the virtual memory hardware?

$($d$)$ The process then attempts to dereference a pointer and perform a memory access. Unfortunately there's

a bug in the code and the pointer points to an invalid memory location that does not have a page table

entry. What signal does the operating system send to the process?