23. ADC Applications- Arduino

What is the voltage on pin A0 of Arduino UNO, if the LED is at its 90% brightness?

const int pinInp = A0;
const int ledOp = 9;

void setup() {
  Serial.begin(9600);
  pinMode(ledOp, OUTPUT);
  analogReference(EXTERNAL);
}

void loop() {
  int analogValue = analogRead(pinInp);
  analogWrite(ledOp,analogValue/4);
  while(1);
}