Procedure: 
Ask a person to choose 1 to 8 cards from a deck. 
Tell the participant to add up the chosen cards. (King, Queen, Jack, and Joker count as 10.) 
In the video, eight cards are chosen. 
Now ask the participant to indicate whether the total of the selected cards appears in A, B, C, or D (above). 
Is the total in red or in black?

Magically predict their total.

Question: How can this prediction be done?