How many variables and reference$-$variables $($in total$)$ have been declared in the following code:

public static void main $($String$[]$ args$)\{$

int number $=0$;

Scanner input $=$ new Scanner$($System$.$in$)$;

final double RATE $=3\mathrm{.}21$;

number $=$ input.nextInt$()$;

System.out.printf$("\%\mathrm{.}2$f$",$ Math.PI $*$ number$)$;

$\}$

A$.4$

B$.2$

C$.1$

D$.3$