Switch

function main(a, b) {
//Input
    let city = a;
    let sales = Number(b);
    let commission = 0;
    let isError = false;

//Table calculations
    switch (city) {
        case 'Sofia':
            if (sales > 0 && sales <= 500) {
                //5%
                commission = sales * 0.05;
            } else if (sales > 500 && sales <= 1000) {
                //7%
                commission = sales * 0.07;
            } else if (sales > 1000 && sales <= 10000) {
                //8%
                commission = sales * 0.08;
            } else if (sales > 10000) {
                //12%
                commission = sales * 0.12;
            } else {
                isError = true;
            }
            break;
        case 'Varna':
            if (sales > 0 && sales <= 500) {
                //4.5%
                commission = sales * 0.045;
            } else if (sales > 500 && sales <= 1000) {
                //7.5%
                commission = sales * 0.075;
            } else if (sales > 1000 && sales <= 10000) {
                //10%
                commission = sales * 0.10;
            } else if (sales > 10000) {
                //13%
                commission = sales * 0.13;
            } else {
                isError = true;
            }
            break;
        case 'Plovdiv':
            if (sales > 0 && sales <= 500) {
                //5.5%
                commission = sales * 0.055;
            } else if (sales > 500 && sales <= 1000) {
                //8%
                commission = sales * 0.08;
            } else if (sales > 1000 && sales <= 10000) {
                //12%
                commission = sales * 0.12;
            } else if (sales > 10000) {
                //14.5%
                commission = sales * 0.145;
            } else {
                isError = true;
            }
            break;
        default:
            isError = true;
            break;
    }

//Output
//Invalid city/sales (-1) == 'error' // toFixed(2)
    if (isError) {
        console.log('error');
    } else {
    console.log(commission.toFixed(2));
    }
}