Figure 37-17 shows two clocks in stationary frame S\" (they are synchronized in that frame) and...

Figure 37-17 shows two  clocks in stationary frame S\" (they are synchronized in that frame) and one clock in moving  frame S. Clocks C₁ and C’₁ read zero when they pass each other. When clocks C₁ and C’₂ pass each other, (a) which clock has the smaller reading and (b) which clock measures a proper time?

Fig. 37-17