$```$

$5.$ Modify$/$fix the following Arduino Mega code. Change the

prescaler to run $4$ times slower. And configure the watchdog

to trigger an interrupt which toggles an LED connected to

board pin $4.$

void setup$()\{$

DDRB ;

WDTCSR $|=(1$ WDCE$)|(1$ WDE$)$;

WDTCSR $=(1$ WDE WDPO$)$;

sei$()$;

$\}$

void loop$()\{$

delay$(1000)$;

$\}$

$```$