Help please I’m stuck, I’m so bad at this…

```
// Write your function here:
const finalGrade = (number1, number2, number3) => {
if ((number1 < 0 || number1 > 100) || (number2 < 0 || number2 > 100) || (number3 < 0 || number3 > 100)) {
return 'You have entered an invalid grade';
}
}
let average = (number1 + number2 + number3) / 3;
if (average >= 0 || average <= 59) {
return 'F';
} else if (average >= 60 || average <= 69) {
return 'D';
} else if (average >= 70 || average <= 79) {
return 'C';
} else if (average >= 80 || average <= 89) {
return 'B';
} else if (average >= 90 || average <= 100) {
return 'A';
}
console.log(finalGrade(60, 70, 75))
```

Shows an error saying number1 is not defined.