axial flow compressor mass flow calculation

Here is the data for W251B11 westinghouse gas turbine 50MW. we have all these parameters but no idea to calculate the mass flow... and we need it very much because we have lesser output from our 2nd turbine which has the same characteristics, same design but 2MW lesser. so by knowing mass flow we might able to confirm that this is compressor problem as mass flow is reduced.

because in compressor efficiency calculations we have 2% less efficiency also even after offline washing on same date. please help me in this regard.

1. ambient air pressure = 985 mBar
2. inlet filter differential pressure = 2.5 in.WC
3. compressor bellmouth differential pressure = 89 in.WC
4. compressor inlet temperature (RTD)= 74.6F
5. exhaust backpressure. = 6.0 in.WC
6. Compressor discharge pressure = 212PSI
7. Compressor discharge temperature = 806.1F