Using the Jar test results shown in Table $1$ to answer the following questions.

$\backslash$table$[[$Beaker$,1,2,3,4,5,6],[$Alum dosage $($mg$/$L$),0,40,50,55,60,65],[$Final turbidity,$13,7,6,6,6,8]]$

a$)$ Determine the optimum dosage $(m\frac{g}{L}).$

b$)$ If the initial turbidity was $30$NTU, calculate the percentage of turbidity removal by this coagulant.

c$)$ For a treatment plant with a capacity of $900\frac{m^3}{d},$ calculate the amount of coagulant in Kilogram consume in one month.