Problem $0.$ Suppose a file contains $200$ bytes of data. A program successfully opens it for both

reading and writing $($i$.$e$.,$ passing the mode O$\_$READWR to open$()),$ and gets back a file descriptor

number fd$.$

a$.$ The program calls read$($fd$,$buf,$70)$ where buf is at least $70$ bytes long. It does something

with the data read from the file, and then repeats the call. Both calls return the exact amount

requested. Then it then calls read$($fd$,$buf,$70)$ a third time. What value will it return?

$($Assume no other program has the file open.$)$

b$.$ Next the program calls write$($fd$,$otherbuffer,$40),$ and the call returns $40.$ Then it calls

read$($fd$,$buf,$40).$ What will the return value from that call be$?$

c$.$ Suppose the programmer needs to read back the last $100$ bytes of the file $($including the ones

just written$).$ What parameters should it invoke lseek$()$ with so that its next read will return

the last $100$ bytes of the file