Q$1.$ Bitwise logical operations $($AND$,$ OR$,$ XOR$)$ can be used to set, clear, or invert bits in a number. Explain how to do each of the following operations with a bitwise logical operation. For example: "bitwise AND with $0$x$55($mask value$)"$

A$)$ For an $8-$bit number, set the bits $4-7$ and leave the other bits unchanged.

B$)$ For a $16-$bit number, invert the top four bits of the number and leave the bottom four bits unchanged.