Grade book challenge JavaScript

We are required to write a function that finds the mean of the three scores passed to it and returns the letter value associated with that grade according to the following table.

Example

const findGrade = (...scores) => {
   const {
      length
   } = scores;
   const sum = scores.reduce((acc, val) => acc + val);
   const score = sum / length;
   if (score >= 90 && score <= 100) {
      return 'A';
   }
   else if (score >= 80 ) {
      return 'B';
   } else if (score >= 70 ) {
      return 'C';
   } else if (score >= 60) {
      return 'D';
   } else{
      return 'F';
   };
}
console.log(findGrade(5,40,93));
console.log(findGrade(30,85,96));
console.log(findGrade(92,70,40));

Output

And the output in the console will be −

F
C
D