 So here's what we've got so far. We know how the y-axis transform and we're assuming that the x and time axes transform linearly. Now we also know that there's no difference between transforming a point from Alice's to Bob's reference frame and transforming a distance between two events from Alice's reference frame to Bob's. So what we're going to do now is we're going to try consider some physical situations where we know what xa, xb, tan, tbr substitute these values in and try and solve for these constants cd, enf. Alice's and Bob's axes are initially aligned and Alice is standing at her origin. Now Alice is holding a stopwatch and at time ta equals zero she starts timing. So that's what our first event is. Alice starting her stopwatch. Now her reference frame moves along and then later on Alice stops her stopwatch. So these are what our two events are. Alice starting her stopwatch is event one and Alice stopping her stopwatch is event two. So the time interval between these events will call delta a in Alice's frame. Now the time Bob measures between these events will call delta tb. So now in terms of v, gamma and delta ta delta tb, one what is delta xa? So if you ask Alice in her frame what is the difference along the x axis between these two events? What would Alice say? Then what is delta xb? What would Bob measure in his coordinates? And how do delta ta and delta tb relate knowing what we know about time dilation?