Two banner ads

Hi
Is it possible to ad two banners on one screen. ?
I tried


void Start()
{
StartCoroutine(ShowBannerWhenReady());
StartCoroutine(ShowBannerWhenReady2());
}

IEnumerator ShowBannerWhenReady()
{
Advertisement.Banner.SetPosition(BannerPosition.BOTTOM_CENTER);
while (!Advertisement.IsReady(placementId))
{
yield return new WaitForSeconds(0.5f);
}
Advertisement.Banner.Show(placementId);
}...

Two banner ads