Write a subroutine MULBY$10$ to multiply the binary number located at R$7$:R$6($known to be less than $10000$d$)$ by $6$ and write the result in R$4$:R$3.$ Do not use the MUL AB instyruction but use only the rotate instructions. All numbers are binary numbers. For example, if R$7$:R$6=0096$h $(150$d$)$ upon the subroutine call, then the subroutine MULBY$10$ will return $03$:$84$h $(900)$ in R$4$:R$3.$