what is displayed by the following code segment?

public class Book $\{$

private double cost, retail;

private boolean fiction;

private void setRetail$()\{$

if$($fiction$)$

retail $=$ cost $*2\mathrm{.}0$;

else

retail $=$ cost $*1\mathrm{.}5$;

$\}$

public Book$($double c$,$ boolean f$)\{$

cost $=$ c;

fiction $=$ f;

retail $=$ cost;

$\}$

public double getRetail$()\{$

setRetail$()$;

return retail;

$\}$

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

Book myBook $=$ new Book$(10\mathrm{.}0,$ true$)$;

System.out.println$($myBook$.$getRetail$())$;

$\}$

a$.12\mathrm{.}0$

b$.18\mathrm{.}0$

c$.24\mathrm{.}0$

d$.$ none of these