function getGrade(score) {
    let grade;
    score <= 30 && score > 25 ? grade='A' : 
    score <= 25 && score > 20 ? grade='B' : 
    score <= 20 && score > 15 ? grade='C' :
    score <= 15 && score > 10 ? grade='D' :
    score <= 10 && score >  5 ? grade='E' :
    grade='F'
    
    return grade;
}