A plant produced $115$ staplers today, it was originally designed to produce $150$ staplers in a day, the equipment can produce $175$ staplers a day, but at that capacity it will overheat after $3$ days of operations. However, the defect rate is minimized when the plant is run at $120$ staplers a day. What is the plant's capacity utilization rate? $($at effective capacity$)$

a$)76\mathrm{.}67\%$

b$)65\mathrm{.}71\%$

c$)95\mathrm{.}83\%$

d$)$ None of the above