All the four entries of the 2 `xx` 2 matrix P = `[[P_11, P_12],[P_21, P_22]]` are nonzero, and one of its eigenvalues is zero. Which of the following statements is true?
`P_11P_22` - `P_12P_21` = 1
`P_11P_22` - `P_12P_21` = -1
`P_11P_22` - `P_12P_21` = 0
`P_11P_22` + `P_12P_21` = 0