Answer based on context:

The original PowerBook 100, 140, and 170 were replaced by the PowerBook 145 (updated to the PowerBook 145B in 1993), PowerBook 160, and PowerBook 180 in 1992. The 160 and 180 having video output allowing them to drive an external monitor. In addition, the PowerBook 180 had a superb-for-the-time active-matrix grayscale display, making it popular with the Mac press. In 1993, the PowerBook 160 was the first PowerBook with a color screen, later followed by the PowerBook 180. In 1994, the last true member of the 100-series form factor introduced was the PowerBook 150, targeted at value-minded consumers and students. The PowerBook 190, released in 1995, bears no resemblance to the rest of the PowerBook 100 series, and is in fact simply a Motorola 68LC040-based version of the PowerBook 5300 (and the last Macintosh model to utilize a Motorola 68k-family processor). Like the 190, however, the 150 also used the 5300 Integrated Drive Electronics-based logic-board architecture. From the 100s 68000 processor, to the 190s 68LC040 processor, the 100 series PowerBooks span the entire Apple 68K line, with the 190 even upgradable to a PowerPC processor.

What year did the PowerBook model come out that was upgradable to a PowerPC processor?