Boa tarde, Jesica.
Pedra: P4 = 4! = 4 . 3 .2 . 1 = 24 anagramas
Castro: P6 = 6! = 6 . 5 . 4 . 3 . 2 . 1 = 720 anagramas
Banana: P62,3 = 6!/ 2! . 3! = 6 . 5 . 4 . 3!/2 . 3! = 60 anagramas
Arroz: P52 = 5!/2! = 5 . 4 . 3 . 2 . 1/2 = 60 anagramas