For each of the following pairs $(A,B)$ of numbers, calculate $A+B,A-B,-A+B,$ and A $-$ B$,$ assuming an $8-$bit two's complement number system. Check the results by decimal arithmetic. Explain any unusual results.

$($a$)01010101,00001010(+{95}_{10},+{75}_{10},-{75}_{10},-{95}_{10})$

$($b$)01101011,00101010($Overflow$,+{65}_{10},-{65}_{10},$ Overflow$)$

$($c$)11101010,00101111(+{25}_{10},-{69}_{10},+{69}_{10},-{25}_{10})$

$($d$)10000000,01111111(-110,$ Overflow, Can't be obtained, Can't be obtained$)$