Consider a production process that produces batteries. A quality engineer has taken $20$ samples, each containing $100$ batteries. The total number of defective batteries observed over the $20$ samples is $200.$ The centerline for the control chart is

a$)0\mathrm{.}03$

b$)0\mathrm{.}04.$

c$)0\mathrm{.}05.$

d$)0\mathrm{.}10.$