plz answer this question

[wail_poet]

the problem is found in student evALUATION page 59 in problem department #28 and the problem as following:

28- U-shaped tube of cross section area 2cm2 has amount of water, 9cm3 of kerosene has been poured in one side, so the height difference of water in the two sides is 3.6cm. find the volume of benzene poured in the other side till the level of water becomes the same in the two sides (pw=1000 kg.m3,pbenzene=900kg/m3) the answer is [8 cm3]
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the steps:

(ph)water=(ph)kerosene so
1000 x 3.6 = pK x 4.5 so pK = 800 kg/m3.
(ph)Benzene=(ph)kerosene so
900 x h = 800 x 4.5 so h benzene = 4 cm so its volume = 4x2=8cm3.
with my regards Mr. WAlid 01004104024