In a Cartesian coordinate system, a steady, incompressible velocity field of a Newtonian fluid is given by
\[
V = u_0 \left( 1 - a y^2 \right) \hat{i}
\]
Here, \( V \) is the velocity vector in m/s, \( \hat{i} \) is the unit vector in the x-direction, \( u_0 \) is a positive, real constant in m/s, and \( a \) is a positive, real constant in m\(^{-2}\). The viscosity of the fluid is \( \mu \) in Pa-s. The absolute value of the pressure gradient (in Pa/m) is