If a,b,ca, b, ca,b,c are in arithmetic progression, which of the following is true?
2b=a+c2b = a + c2b=a+c
b2=acb^2 = acb2=ac
b−a=c−bb - a = c - bb−a=c−b
a+b+c=3ba+b+c = 3ba+b+c=3b