Write down the elementary 4 4 permutation matrix (a) P1 that permutes the second and fourth

Question:

Write down the elementary 4 × 4 permutation matrix
(a) P1 that permutes the second and fourth rows, and
(b) P2 that permutes the first and fourth rows.
(c) Do P1 and P2 commute?
(d) Explain what the matrix products P1 P2 and P2 P1 do to a 4 × 4 matrix.