calculateSumAndVat

function sumVat(arr) {
    let sum = 0;

    for(let i = 0; i < arr.length; i++) {
        sum += arr[i];
    }

    console.log(`sum = ${sum}`);
    console.log(`VAT = ${sum * 0.2}`);
    let total = sum + sum * 0.2;
    console.log(`total = ${total}`);
}