// Arg: students score, total possible Mark
// 15/20 -> You got a C (75%)
// A: 90-100, B 80-89, C 70-79, D 60-69, F 0-59

let calcGrade = function (score, totalScore) {
    let percent = score / totalScore * 100;
    let letterGrade = '';
    if (percent >= 90) {
        letterGrade = 'A';
    } else if (percent >= 80 && percent <= 89) {
        letterGrade = 'B';
    } else if (percent >= 70 && percent <= 79) {
        letterGrade = 'C';
    } else if (percent >= 60 && percent <= 69) {
        letterGrade = 'D';
    } else {
        letterGrade = 'F';
    }

    return `You got a ${letterGrade} (${percent}%)`
}

let result = calcGrade(15, 20)
console.log(result);