What is the output of the following code segment?

double $a=21\mathrm{.}5$;

int $b=6$;

printf $("\%$f $",$ a$)$;

printf$("\%$d$",,b$

$216$

An error will occur due to all the spaces.

ab

$21\mathrm{.}56$

$21\mathrm{.}56\mathrm{.}0$