please help, some basic physic formulae i think

i need ur help regarding this, ive tryed by my self but im soo sure that ive done wrongly

here it comes
the figure shows that how i oversizing the hex 1/2" nut by oversizing machine. the pressure which is 3.5kg/mm sq is pushes the nut thru the tapper of a 100 mm length. how can i determine the time taken,t for the nut to going thru the 100mm tapper

here is the detail that may required

size of nut: 1/2 inch hexagonal nut (internal dia of nut = 1/2 inch)
pressure, P: 3.5kg/mm sq
tapper length,L: 100mm
Power of machine: 5HP
Speed: 750 rpm
time, t = ???

ive once try to determine the force exist by P=F/A:
then once i get the F, ive determine the work done which is W=F x S;
lastly ive tried to find the time,t by using P= W/t which is P is a power of machine while W is a work done

but im not satisfied with the answer that i got,

can anybody correct me if im wrong or giving me for some tips or correct formulae on how to done it

i would be greatly thanks