Bob is moving to the right (positive x direction) in his spaceship at a velocity v (such that the value of the Lorentz factor is 2), and Alice is observing him. Each has their own lattice of clocks and measuring systems, which can be represented in two spacetime diagrams on the same plot, one for Bob’s frame of reference and one for Alice’s. Assume that the axes on Alice’s plot are at right angles to each other (horizontal and vertical) and Bob’s are at different but appropriate angles. If Alice observes a set of three flash bulbs at positions xA = 9, 13, and 24, and they all flash at tA = 7.3, which flash would occur first in Bob’s frame of reference?