Combinations: We have 21 balls in total. We have 7 different sizes of balls. Each ball is colored in 1 of 3 colors. (Blue, Pink, Black). In summary: there are 7 different sizes of pink balls, 7 different sizes of blue balls, 7 different sizes of black balls. All in total, we have 21 balls. Compute the combinations and give a brief explanation your thinking process: 1. Select 3 balls. The balls selected are all the same color. 2. Select 3 balls. No two of the balls of the same size. 3. Select 3 balls. The color of the 3 balls selected are blue, pink, black and no two balls selected are of the same size