Example 2. 8 different elements are arranged in two rows, with 4 elements in each row, where 2 specific elements must be in the front row, and 1 specific element must be in the back row. How many arrangements are possible? (Question 12 (2), page 158)
Example 2 solution. For 2 elements to be arranged in the front row, first arrange them, there are $\mathrm{P}_{4}^{2}$ arrangements, for a certain element to be arranged in the back row, also arrange it first, there are 4 arrangements, the remaining 5 elements can be arranged in the remaining 5 positions in any order, there are $5!$ arrangements, so there are a total of $\mathrm{P}_{4}^{2} \times 4 \times 5!=5760$ arrangements.