Please explain the features $($including advantages and disadvantages$)$ For the following three independent file systems, please draw the final

file system of $U$ looks like after the following two mountings:

$(1)$ mounting S$1$:$/$user$/$shared over U:$/$user$/$local

$(2)$ mounting S$2$:$/$user$/$dir$2$ over U:$/$user$/$local$/$dir$1$