The average age of 25 students in a group is 12 years. when teacher's age is included to it, the average increases by one.What is the teacher's age in years?  Choose the correct choice from the following choices.
A) 31	B) 38	C) 39	D) 40	E) 57
age of the teacher=(26*13-25*12)= 
<gadget id="calculator">(26*13-25*12)</gadget>
<output>38</output>
38 years.   ANSWER:38
<result>B</result>
The average age of 25 students in a group is 12 years. when teacher's age is included to it, the average increases by one.What is the teacher's age in years?