In the global sum problem that we discussed in class, in lecture $1,$ if we assume that there is a variable called my$\_$rank $($local to each core$)$ that gives each core a unique rank from $0$ to p$-1($for p cores$),$ devise an expression to calculate my$\_$first$\_$i and my$\_$last$\_$i assuming:

a$.$ n is divisible by p and n $>$ p$.$ b$.$ n is not divisible by p$.$