If the average (arithmetic mean) of a and b is 120, and the average of b and c is 150, what is the value of a − c?	Choose one.
A) −60	B) −100	C) 100	D) 135	E) It cannot be determined from the information given
a+b = 240   b+c = 300   a-c = -60.   IMO option −60.
<result>A</result>
If the average (arithmetic mean) of a and b is 120, and the average of b and c is 150, what is the value of a − c?