Can mach number increase from 1.8 to 1.22 in Fanno flow?

[Urmi Roy]

In a problem in our book, it says that the mach number in a constant area duct with friction (Fanno flow), the mach number increases from 1.8 to 1.22...however, from the Fanno line, its very clear that in the supersonic region, mach number always decreases along the flow...is there some kind of error?

 

[Urmi Roy]

Sorry, lol...I guess I must be too tensed up with exams...its ok, since mach number decreases from 1.8 to 1.22!