If the average (arithmetic mean) of a and b is 110, and the average of b and c is 170, what is the value of a − c?  Choose the correct choice from the following choices.
A) −120  B) −100  C) 100  D) 135  E) It cannot be determined from the information given
a+b = 220   b+c = 340   a-c = -120.   IMO option −120.
<result>A</result>
If the average (arithmetic mean) of a and b is 110, and the average of b and c is 170, what is the value of a − c?