$(1pt)$ Add $(-9_{10})+(-{11}_{10})$ in binary using $2\text{'}$s complement representation. Use a word length

of $6$ bits $($including the sign bit$)$ and indicate whether an overflow occurs. Convert the result

of this addition back to decimal.

$(2$ pts$)$ Design the $4421$ weighted code for decimal digits. Use a table to show consecutive

decimal digit and the corresponding binary numbers. Is it possible to have two alternative

representations for any of the decimal digits? If yes, then explicitly list all these alternatives

and explain how many possible codes could be designed.