A certain stock exchange designates each stock with a two-letter 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 using only the vowels A, E, I, O, or U?  Options:
A) 110
B) 120
C) 130
D) 140
E) 150
The number of two-letter codes is  5*5= 
<gadget id="calculator"> 5*5</gadget>
<output>25</output>
25.   The number of three-letter codes is  5*5*5= 
<gadget id="calculator"> 5*5*5</gadget>
<output>125</output>
125.   The total number of codes is   25+125= 
<gadget id="calculator">  25+125</gadget>
<output>150</output>
150.   The answer is 150.
<result>E</result>
A certain stock exchange designates each stock with a two-letter 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 using only the vowels A, E, I, O, or U?