39. 5583-!-item-!-187;#058&004668
A certain stock exchange designates each stock with a one-, two-, or three-letter code, where each letter is selected from the 26 letters of the alphabet. If the letters may be repeated and if the same letters used in a different order constitute a different code, how many different stocks is it possible to uniquely designate with these codes?
(A) 2,951
(B) 8,125
(C) 15,600
(D) 16,302
(E) 18,278
Answer: (E)
請問總共幾碼的Code???
倒底是怎麼排出來的組合呢???
煩請好心人