function hitungHPP() {
  let harga = parseFloat(document.getElementById('harga').value) || 0;
  let qty = parseFloat(document.getElementById('qty').value) || 0;
  let ongkir = parseFloat(document.getElementById('ongkir').value) || 0;
  let tenaga = parseFloat(document.getElementById('tenaga').value) || 0;
  let operasional = parseFloat(document.getElementById('operasional').value) || 0;
  let margin = parseFloat(document.getElementById('margin').value) || 0;

  let hpp = (harga * qty) + ongkir + tenaga + operasional;
  let jual = hpp + (hpp * margin / 100);
  let laba = jual - hpp;

  document.getElementById('hpp').innerHTML = "Rp " + hpp.toLocaleString();
  document.getElementById('jual').innerHTML = "Rp " + jual.toLocaleString();
  document.getElementById('laba').innerHTML = "Rp " + laba.toLocaleString();
}