We are given that P(net) = 1 atm
Hence , p(H20) + p(N2) = 1 atm
P(H20) = 0.3 atm
Let volume of the old vessel be V
And volume of new vessel be V/3
But water is incompressible
So we know that p(H20) = constant = 0.3 atm
Therefore , by the following relation we can get our answer,
P is inversely proportional to volume (Boyles law)
We can say that if v decreases by 3 times then p(N2) increases by 3 times
Hence, P(net) = 3*P(N2) + p(H2O) = 2.1 + 0.3 = 2.4 atm