15000-3500= 11500Kg
11500/2150=5,348 hrs = 5h 20min ( = 5.34883... hours, or 5.349 hrs to 3 decimal places)
O= 425-30= 395Kt
H= 430+20= 450Kt
Formula: PSR= E H/(O+H)
5,349*450/(395+450) = 2h 50 min ( = 2.84857 ... hours, or 2.849 hrs to 3 decimal places .... = 2 hrs 50.94 mins ... )