Pls sir ans urgently:

(a) When floating,

Mass of water displaced = Mass of floating test tube = 20 g

Therefore, Mass of water displaced = 20 g

(b)  Mass of water displaced = length immersed  x area of cross-section of tube x  density of water

or,  20 = 10 x A x 1                                       (since, density of water = 1 g cm^-3) 

Therefore, Area of cross-section of the test tube (A) =  2 cm²

(c) RD (Relative density) of kerosene = $\frac{\mathrm{length} \mathrm{of} \mathrm{test} \mathrm{tube} \mathrm{immersed} \mathrm{in} \mathrm{water}}{\mathrm{Length} \mathrm{of} \mathrm{test} \mathrm{tube} \mathrm{immersed} \mathrm{in} \mathrm{kerosene}}=\frac{10}{12}=\frac{5}{6}=0.833$