Lots of fun to play with the formulas... But, the fly in the ointment
here is that the airspeed filed by the pilot is a canned number and has
nothing to do with reality... I fly IFR, I file the same airspeed - 130
kt - for all flights regardless of load, altitude, and what the power
setting winds up to be... If the actual airspeed in your problem is
within 15% of the filed number you will be lucky...

denny