75nm at original ground speed (115kts) would take 39.1 minutes.  

Aircraft has covered 75nm in 40.6 minutes = ground speed 111kts.  

Remaining distance to run is 250 – 75 = 175nm and at revised ground speed of 111kts this will take 94.6 minutes.  

Total elapsed time = 40.6 + 94.6 = 135.2 minutes (2h15m).  

Departure time is 0900 add elapsed time 2h15m, ETA = 1115.