a$)$ Explain the difference between Internal and External fragmentation. Use a diagram to help with your explanation b$)$ Consider a logical address space of $16$ pages of $512$ words each mapped onto a physical memory of $128$ frames. $($assume page and frame size are the same assume a word $=8-$bit byte if needed$)$ How many bits are needed to represent the logical address? How many bits are needed to represent the physical address? c$)$ On average, how much system frag XW$17$ mentation would you expect to occur using paging? d$)$ What type of fragmentation occurs when paging is used internal$/$external$)?$