$(25$ pts$)$ After the following program is executed, what is the content of $R4$ in hex?

ORG $\frac{?}{OO}H$

MOV R$1,$ #$12H$

MOV R$2,$ #$36$H

MOV R$3,$ #$44$H

MOV A$,$ R$1$

MOV $B,R2$

LCALL SUM

MOV $B,R3$

LCALL SUM

MOV R$4,$ A

SUM: $,$ ADD A$,$ B

RET

END

$R4=$