Let u(x, y) be the solution of \(\frac{\partial^{2} u}{\partial x^{2}}+\frac{\partial^{2} u}{\partial y^{2}}=64\) in the unit disc {(x, y) | x² + y² < 1} and such that u vanishes on the boundary of the disc. Then \(u\left(\frac{1}{4}, \frac{1}{\sqrt{2}}\right)\) is equal to