Clearly, the path of the Kripke structure always satisfies a,b, and c. It is therefore never the case that b holds before c, and therefore [b SB c] is always false. Same way, it is never the case that a holds before b, and therefore [a SB b] is always false. Thus, we may now consider the formulas
The first formula is obviously true, since (for example) at the first point of time, "a" holds, and that holds before "false" becomes true (which is never the case). The second formula is however false, since false cannot become true, but it should, and it should even become true before c holds, but that is already true at the initial point of time.
