The apparent weight is caused by the upthrust force acting against the rock's weight. The upthrust force is equal to the weight of water that has been displaced by the rock.
So, U = Vpg
Where U is the upthrust force, V is the volume of the rock, p is the density of water, and g is the acceleration due to gravity.
The upthrust force is also equal to the difference between the weight of the rock outside the water, and the apparent weight of the rock submerged in water, so:
U = 1888 - 1038 = 850 N
Rearrange the original equation to make V the subject:
V = U/pg
Sub in values to find V:
V = 850/(997 • 9.81)
V = 850/9780.57
V = 0.086907 m^3
Therefore V = 0.09 m^3 (to the nearest hundredth)