function sumOf3Numbers(input) {
    let sum = 0;
    input = Number(input);
   for(let i=0; i<input.length; i++) {
       sum += input[i];
   }
       let vat = sum * 0.20;
       let total = sum * 1.20;
       console.log("sum = " + sum);
       console.log("VAT = " + vat);
       console.log("total = " + total);

}
console.log(sumOf3Numbers(['3.5','4.5','1.3']));