UnityAds Use both Rewarded and Interstitial Video Ad

Hi everyone, I implemented Unity Ads according to the Manual and it is working. However, I try to use both Reward Video Ad and Interstitial Video Ad and there seems to be an Override, because both functions reward the Player.
For testing the Functionality, I have two Buttons in my scene, the first one is connected to DisplayInterstitialAD() and the second one is connected to DisplayRewardVideoAD(). No matter which one is called, they both call OnUnityAdsDidFinish(...) and thus the Reward Function.
Is it wrong to implement both Methods in one Script? I know one Workaround would be to use a bool connected to the buttons, but I think that I implemented it wrong and Unity has another solution for combining the two ad formats, right?

This is the Script:

using UnityEngine;
using UnityEngine.Advertisements;

public class AdManager : MonoBehaviour, IUnityAdsListener
{
    public static AdManager instance;
    public bool TestMode = true;

    string game_ID = "xxxxxxx";
    string myPlacementId = "rewardedVideo";

    private void Start()
    {
        Advertisement.Initialize(game_ID, TestMode);
        Advertisement.AddListener(this);
    }

    public void DisplayInterstitialAD()
    {
        Advertisement.Show();
    }

    public void DisplayRewardVideoAD()
    {
        Advertisement.Show(myPlacementId);
    }


    public void OnUnityAdsDidFinish(string placementId, ShowResult showResult)
    {
        // Define conditional logic for each ad completion status:
        if (showResult == ShowResult.Finished)
        {
            PayReward_1();
        }
        else if (showResult == ShowResult.Skipped)
        {
            // Do not reward the user for skipping the ad.
        }
        else if (showResult == ShowResult.Failed)
        {
            Debug.LogWarning("The ad did not finish due to an error.");
        }
    }

    public void PayReward_1()
    {
        //Paying the Reward to the Player
    }
}

Within your OnUnityAdsDidFinish method do this

if(placementId.Equals(myPlacementId))
{
    if(showResult == ShowResult.Finished)
    {
        PayReward_1();
    }
}

Ok I found the solution. I have to use two different Placement IDs, which I generate in the Unity Dashboard. And then I initialize and call them like this:

string PlacementId_reward = "rewardedVideo";
string PlacementId_interstitial = "interstitial";
public void DisplayInterstitialAD()
{
    Advertisement.Show(PlacementId_interstitial);
}

public void DisplayRewardAD()
{
    Advertisement.Show(PlacementId_reward);
}

For detecting the Reward I can then use the solution of Kofiro posted above. Thanks!