Problem med en funktion, den ger #undefined

var scores = [60, 50, 60, 58, 54, 54, 58, 50, 52, 54, 48, 69, 34, 55, 51, 52, 44, 51, 69, 64, 66, 55, 52, 61, 46, 31, 57, 52, 44, 18, 41, 53, 55, 61, 51, 44];
var costs = [.25, .27, .25, .25, .25, .25, .33, .31, .25, .29, .27, .22, .31, .25, .25, .33, .21, .25, .25, .25, .28, .25, .24, .22, .20, .25, .30, .25, .24, .25, .25, .25, .27, .25, .26, .29];

function printAndGetHighScore(scores){
    var highScore = 0;
    var output;

    for (var i = 0; i < scores.length; i++){
        output = "Bubble solution #" + i + " score: " + scores[i];
        console.log(output);
        if (scores[i] > highScore){
            highScore = scores[i];
        }  
    }

    return highScore;   
}
function getBestResults(scores, highScore){
    var bestSolutions = [];
    for(var i = 0; i < scores.length; i++){
        if(scores[i] == highScore){
            bestSolutions.push(i);  
        }
    }
    return bestSolutions;
}
function getMostCostEffectiveSolution(scores, costs, highScore){
    var cost = 100;
    var index;

    for (var i=0; i< scores.length; i++){
        var costsIndex = costs[i];
        if(scores[i]>=highScore && costsIndex < cost){
            index = scores[i];
            cost = costs[i]    
        }
    }
    return index;
}

var mostCostEffective = getMostCostEffectiveSolution(scores, costs, highScore);


var highScore = printAndGetHighScore(scores);
console.log("Bubbles tests: " + scores.length);
console.log("Highest bubble score: " + highScore);

var bestSolutions = getBestResults(scores, highScore);
console.log("Solutions with the highest score: " + bestSolutions);
console.log("Bubble Solution #" + mostCostEffective + " is the most cost effective");

var mostCostEffective = getMostCostEffectiveSolution(scores, costs, highScore);


var highScore = printAndGetHighScore(scores);

var highScore;