Suppose that $A_3{A}_2{A}_1{A}_0$ is a $4-$bit signed binary number $($using $2$ s complement for

negative numbers$).$ please design a method to convert it to an $8-$bit signed number. Use

$B_7{B}_6{B}_5{B}_4{B}_3{B}_2{B}_1{B}_0$ to represent the result and write down the logic functions. $(5$pts$)$