Answer:
Mass of water displaced = 1.6 kg 
Step-by-step explanation:
given data 
Mass of brick m = 4kg 
Density of water d₁ = 1000kg/m³
Density of brick d₂ = 2.5 g/cm³ = 2500 kg/m³
solution
we get here first volume of brick that is 
volume of brick = m ÷ d₂ ..................1
put here value and we get 
volume of brick = 4 ÷ 2500
volume of brick = 0.0016 L 
and 
we will use here Archimedes' Principle formula of the buoyant force
as buoyant force = the weight of the liquid displaced by an object
so now we get here Buoyant Force that is express as
Buoyant Force = v × d₁ × g ........................2
put here value 
Buoyant Force = 0.0016 × 1000 × 9.8 
Buoyant Force = 15.68 Newtons
so 
Buoyant Force = Weight of the water displaced .................3
Buoyant Force = Mass of water displaced × g
and 
weight = mass × acceleration due to gravity .......................4
so put here value and we will get
15.68 = mass of brick × 9.8
Mass of water displaced = 1.6 kg