function setDivVisibility(divName, imgName, turnOn) {
  var div = document.getElementById(divName);
  var img = document.getElementById(imgName);

  div.style.display = (turnOn) ? 'block' : 'none';
  img.src = (div.style.display == 'none') ? './images/right-arrow.png' : './images/down-arrow.png';
}

function toggleDivVisibility(divName, imgName) {
  var div = document.getElementById(divName);
  
  var turnOn = (div.style.display == 'none') ? true : false;
  
  setDivVisibility(divName, imgName, turnOn);
}