Find the optimal solution for the following problem. Note: Round your answers to $3$ decimal places.

Maximize $C=,13x+9y$

subject $to6x+11y18$

$,16x+21y41$

and $x0,y0$

a$.$ What is the optimal value of $x?$

$x$

b$.$ What is the optimal value of $y?$

$y$

c$.$ What is the maximum value of the objective function?