The content of the top of the memory stack is $x1.$ The content of the stack pointer SP is $Y1.$ A two word call subroutine instruction is located in memory at address $1120$ followed by the address field of $x2$ at location $1121.$ What are the contents of PC$,$ SP$,$ and the top of the stack:

a$)$ Before the call instruction is fetched from the memory

b$)$ After the call instruction is executed

c$)$ After the return from subroutine