How many positive integers less than 120 are there such that they are multiples of 13 or multiples of 12 but not both?  Choose the correct answer:
A) 13  B) 19  C) 15  D) 16  E) 17
for 13: 13...117=13*9= 
<gadget id="calculator">13*9</gadget>
<output>117</output>
117   for 12: 12...120=12*10= 
<gadget id="calculator">12*10</gadget>
<output>120</output>
120   but there is one integer 13*12. so   N=(9)+(10)= 
<gadget id="calculator">(9)+(10)</gadget>
<output>19</output>
19   19
<result>B</result>
How many positive integers less than 120 are there such that they are multiples of 13 or multiples of 12 but not both?