The word ''chemika'' has 7 different letters.
So we need to select 7 square boxes for these 7 different letters to be placed. Selection of 7 square boxes can be done in the following ways:
Case 1: 1 from first row, 1 from second row, 1 from third row and 4 from the fourth row 2C1 × 2C1 × 3C1 × 4C4 = 2 × 2 × 3 × 1 = 12 ways
Case 2: 1 from first row, 1 from second row, 2 from third row and 3 from the fourth row 2C1 × 2C1 × 3C2 × 4C3 = 2 × 2 × 3 × 4 = 48 ways
Case 3: 1 from first row, 1 from second row, 3 from third row and 2 from the fourth row 2C1 × 2C1 × 3C3 × 4C2 = 2 × 2 × 1 × 6 = 24 ways
Case 4: 1 from first row, 2 from second row, 1 from third row and 3 from the fourth row 2C1 × 2C2 × 3C1 × 4C3 = 2 × 1 × 3 × 4 = 24 ways
Case 5: 1 from first row, 2 from second row, 2 from third row and 2 from the fourth row 2C1 × 2C2 × 3C2 × 4C2 = 2 × 1 × 3 × 6 = 36 ways
Case 6: 1 from first row, 2 from second row, 3 from third row and 1 from the fourth row 2C1 × 2C2 × 3C3 × 4C1 = 2 × 1 × 1 × 4 = 8 ways
Case 7: 2 from first row, 1 from second row, 1 from third row and 3 from the fourth row 2C2 × 2C1 × 3C1 × 4C3 = 1 × 2 × 3 × 4 = 24 ways
Case 8: 2 from first row, 1 from second row, 2 from third row and 2 from the fourth row 2C2 × 2C1 × 3C2 × 4C2 = 1 × 2 × 3 × 6 = 36 ways
Case 9: 2 from first row, 1 from second row, 3 from third row and 1 from the fourth row 2C2 × 2C1 × 3C3 × 4C1 = 1 × 2 × 1 × 4 = 8 ways
Case 10: 2 from first row, 2 from second row, 1 from third row and 2 from the fourth row 2C2 × 2C2 × 3C1 × 4C2 = 1 × 1 × 3 × 6 = 18 ways
Case 11: 2 from first row, 2 from second row, 2 from third row and 1 from the fourth row 2C2 × 2C2 × 3C2 × 4C1 = 1 × 1 × 3 × 4 = 12 ways
Total number of ways of selection of 7 square boxes = 12 + 48 + 24 + 24 + 36 + 8 + 24 + 36 + 8 + 18 + 12 = 250
For each selection of 7 square boxes, the number of arrangements of 7 different letters = 7! = 5040
Hence , Total number of arrangements = 5040 × 250 = 1260000

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