From equilibrium of vertical forces, we know that the buoyant force acting on Titanic must equal to its weight, because Titanic is floating. Therefore we first have to calculate the weight of Titanic.
Mass of Titanic (in kg) = 50,000 tonnes 1000 = 5 107kg
Weight of Titanic = 5 107kg 10 m/s = 5 108N
There, we already found the first answer - the magnitude of buoyant force is 5 108N.
To find the second answer, we rely upon Bernoulli's principle which state that the magnitude of the buoyant force must equal the weight of the displaced liquid. We therefore know the weight of the displaced seawater and can equate it as such:
Weight of displaced seawater = 5 108N
(Mass of displaced seawater) 10 m/s = 5 108N
(Volume of displaced seawater) 1025 kg/m 10 m/s = 5 108N