Assume for arithmetic, load$/$store$,$ and branch instructions, a processor running at $2$ Ghz has CPIs of $2,10,$ and $4,$ respectively. Also assume that a program has $200$ million arithmetic instructions, $30$ million load$/$store instructions, and $2$ million branch instructions.

You have the following options to optimize only one of the three instructions: $(1)$ reduce the time of arithmetic instructions by $30\%$

$(2)$ reduce the time of load$/$store instructions by $45\%$

$(3)$ reduce the time of branch instructions by $90\%$

Apply Amdahl$$s law to calculate the overall speedup of each option. Which option is the best one?