b$)$ In the following ARM$9$ program, there are two examples of 'data forwarding' and one further example of a 'read$-$after$-$write' hazard that results in an interlock. Identify all three.

Mnemonic

MOV r$1,$ #$0$x$0004$A$000$

MOV r$2,$ #$0$x$00003$BC$0$

MOV $r0,r1,$ LSL #$4$

SUB $r3,r2,r1$

ADD $r4,r1,r2$

RSB $r5,r4,r0$

MOV r$6,$ #$0$x$000002$E$4$

MOV r$7,$ #$0$x$0002$E$400$

ADDr$2,r1,r0$

Comment

; move $0$x$0004$A$000$ into r$1$

; move $000003BC0$ into r$2$

; left shift $r1$ by $4$ bits

; subtract $r1$ from $r2$

; add $r1$ and $r2,$ sum in $r4$

; subtract r$4$ from r$0$

; move $0$x$000002$E$4$ into r$6$

; move $0$x$0002$E$400$ into $r7$

; add $r1$ and $r0,$ sum in $r2$