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?	Choose the correct option.
A) 2951
B) 8125
C) 15600
D) 16302
E) 18278
Remember that Numbers can be repeated.   Number of 1 Digit Codes = 26   Number of 2 Digit Codes = 26 * 26= 
<gadget id="calculator">26 * 26</gadget>
<output>676</output>
676   Number of 2 Digit Codes= 26 * 26 * 26= 
<gadget id="calculator">26 * 26 * 26</gadget>
<output>17_576</output>
17576   Total= 26 + 676 + 17576= 
<gadget id="calculator">26 + 676 + 17576</gadget>
<output>18_278</output>
18278   ANS:18278
<result>E</result>
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?