What is the probability of randomly selecting an arrangement of the letters of the word "MEDITERRANEAN" in which the first letter is E and the last letter is R?
Choose the correct answer.
A) 1 / 13 B) 1 / 20 C) 1 / 26 D) 1 / 50 E) 1 / 100

Rationale: there are 13 letters in mediterranean , out of which e appears thrice , n appears twice , a appears twice , and r appears twice . the number of arrangements of mediterranean is therefore 13 ! / 3 ! 2 ! 2 ! 2 ! the number of arrangements in which the first letter is e and the last letter is r is 11 ! / 2 ! 2 ! 2 ! ( we are left with 11 letters out of which e appears twice , n appears twice and a appears twice ) . p = ( 11 ! / 2 ! 2 ! 2 ! ) / ( 13 ! / 3 ! 2 ! 2 ! 2 ! ) = 11 / ! 2 ! 2 ! 2 ! ∗ 3 ! 2 ! 2 ! 2 ! / 13 ! = 3 ! / 12 ∗ 13 = 1 / 26 answer : c .
Answer: C