blinking led while servo is turning arduino

Question

I have a code here that turn servo motor back and forth and i want to add blinking led while servo motor is turning.
How do i apply it?

here's the code

#include <Servo.h>

Servo servo;

void setup()
{
  pinMode(4, OUTPUT);
  servo.attach(9);
}

void loop()
{
    servo.write(180);        
    delay(2000); 
    blink();
    servo.write(0);        
    delay(2000); 
    blink(); 
  }

  void blink() {
  digitalWrite(13, HIGH);
  delay(100); 
  digitalWrite(13, LOW);
  delay(100);
}