Codecademy - finalGrade

// Write your function here:
let finalGrade = (n1, n2, n3) => {
  if((n1 < 0 || n2 < 0 || n3 < 0) ||
      n1 > 100 || n2 > 100 || n3 > 100){
    return 'You have entered an invalid grade.';
  }
  let total = n1+n2+n3;
  let avg = total / 3;
    if(avg <= 59){
      return 'F';
    } else if (avg <= 69) {
      return 'D';
    } else if (avg <= 79){
      return 'C';
    } else if (avg <= 89){
      return 'B';
    } else if (avg <= 100){
      return 'A';
    }
}


console.log(finalGrade(99, 92, 95))