A two-dimensional incompressible frictionless flow field is given by $\overrightarrow{u} = x \hat{i} – y \hat{j}$. If $\rho$ is the density of the fluid, the expression for pressure gradient vector at any point in the flow field is given as

1. $\rho(x \hat{i}+y \hat{j})$
2. $– \rho(x \hat{i}+y \hat{j})$
3. $\rho(x \hat{i} – y \hat{j})$
4. $– \rho(x^2 \hat{i}+y^2 \hat{j})$