Standing at rest in the Earth reference frame, you observe two events, also at rest in that reference frame, occurring at these coordinates: event $1$: x$1$x$1=25$ kmkm $,$ y$1$y$1=5\mathrm{.}0$ kmkm$,$ z$1$z$1=0,$ t$1$t$1=20$ ss ; event $2$: x$2$x$2=55$ kmkm $,$ y$2$y$2=5\mathrm{.}0$ kmkm$,$ z$2$z$2=0,$ t$2$t$2=35$ ss $.$