code: function getAvailabilitiesForDuration(duration, availabilities) {
      const durationAvailabilities = [];
      let startTime = '10:00';
      while (startTime !== '17:00') {
          if (availabilities.indexOf(startTime) !== -1) {
              if (duration === 30) {
                  durationAvailabilities.push(startTime);
              } else if (availabilities.indexOf(incrementTimeByThirtyMins(startTime)) !== -1) {
                  durationAvailabilities.push(startTime);
              }
          }
          startTime = incrementTimeByThirtyMins(startTime);
      }
      return durationAvailabilities;
  }
docs: Helper function to return the windows of availability of the given duration, when provided a set of 30 minute windows.