( 1)P=F/S=G/a？ =64N/(0.2m)？ =3200Pa a is the side length.

(2)VA=(0.2m)？ VB=(0.3m)？

VA/AB=8/27

mA/mB=GA/AB= 1

ρA:ρB=mA/VA:mB/VB=27:8

(3) After cutting off H, the gravity of the remaining part is g' = m' g = ρ v' g = ρ a? (a-h)g

P'=G'/a？ =ρ(a-h)g

PA'=ρA(0.2 hours) g PB'=ρB(0.3 hours) g.

PA'/PB'=ρA(0.2 hours) /ρB(0.3 hours) =27(0.2 hours) /8(0.3 hours)

① Pa' = Pb' when 27 (0.2-h) = 8 (0.3-h), that is, h=3/ 19m.

② when pa' > Pb' is 27 (0.2-h) > 8 (0.3-h), that is, h < 3/ 19m.

③ Pa' < Pb' at 27 (0.2 hours) < 8 (0.3 hours), that is, 3/19m > h > 0.2m.