[byearthithatius]

Token-based Gemini is 4 seconds of thinking:

Okay, let's break this down using the principle of heat transfer (specifically Newton's Law of Cooling):

    Heat loss is faster when the temperature difference is greater. A very hot object loses heat to cool surroundings much faster than a warm object.

    Option 1: Add milk immediately.

        You instantly lower the coffee's temperature by mixing it with cold milk.

        Now, this warmer (not hot) mixture sits for 2 minutes. Because the temperature difference between the mixture and the room is smaller, it cools down more slowly over those 2 minutes.

    Option 2: Let it sit for 2 mins, then add milk.

        The very hot coffee sits for 2 minutes. Because the temperature difference between the hot coffee and the room is large, it loses heat more quickly during these 2 minutes.

        After 2 minutes of rapid cooling, you then add the cold milk, lowering the temperature further.

Conclusion:

To get the coffee to the lowest temperature, you should choose Option 2: Let it sit for 2 mins, then add the cold milk.