(a)[1]
Find the number of distinct arrangements of the $9$ letters in CROCODILE.
(b)[3]
Find the number of distinct arrangements of the $9$ letters in CROCODILE with a C at each end and with the two Os separated.
(c)[3]
Find the number of selections of $4$ letters from the $9$ letters in CROCODILE for which the number of Cs is different from the number of Os.
(d)[3]
Find the number of ways the 9 letters in CROCODILE can be split into three groups of three letters each, if the two Cs have to be in different groups.