This question was poorly attempted and the performance was low. Many candidates tilled to use upthrust which Is (10.5 - 6.8) rather majority of them used 6 8 directly for the division Some candidates erroneously stated that
Relative density = Extension in air
Extension loss in water
The expected answer is:
R.D 38    =    Weight of body in air
               Upthrust (in water)
NOTE: F = kx
=     K(10.5)
    K( 10.5-6.8)
105
3.1
=      2.84