text: let calculateBtn = document.getElementById('calculate'),
      sellingPriceInput = document.getElementById('selling-price'),
      cogsInput = document.getElementById('cogs'),
      grossMarginInput = document.getElementById('gross-margin'),
      salesMarketingInput = document.getElementById('Sales-marketing'),
      operationCostInput = document.getElementById('operation-cost'),
      netMarginInput = document.getElementById('net-margin'),
      sellingValue, cogsValue, grossMarginValue, salesMarketingValue, operationCostValue,
      netMarginValue;
  
  function calculate() {
  
      sellingValue = sellingPriceInput.value;
  
      cogsValue = cogsInput.value;
      grossMarginValue = sellingValue - cogsValue;
      grossMarginInput.value = grossMarginValue;
  
      // console.log(grossMarginValue);
      salesMarketingValue = salesMarketingInput.value;
      // console.log(salesMarketingValue)
      operationCostValue = operationCostInput.value;
      netMarginValue = grossMarginValue - salesMarketingValue - operationCostValue;
      netMarginInput.value = netMarginValue;    
  
      // console.log('hello');
  }
  
  
  calculateBtn.addEventListener('click', calculate);
  
  