Since B ages 10 years between E1 and E6, B, while in the outgoing frame, will find that A ages 5 years between E1 and E2, and thus is 25 at E2. Similarly, B, while in the incoming frame, will find that A ages 5 years between E4 and E5, and thus (since A is 60 at E5) is 55 at E4. The point is that although B can use the standard time-dilation formula while in any one inertial frame, when changing from the outgoing to the incoming frame B must take account of the fact that the event in A’s life that is simultaneous with the turnaround has jumped 30 years ahead. (For a discussion that does not rely on a particular numerical example, see Janis, 1983a.)