The complex numbers \(u\) and \(w\) are defined by \(u=2e^{\pi i/4}\) and \(w=3e^{\pi i/3}\).

(a) Find \(\dfrac{u^2}{w}\), giving your answer in the form \(re^{i\theta}\), where \(r>0\) and \(-\pi<\theta\le\pi\). Give the exact values of \(r\) and \(\theta\). [3]

(b) State the least positive integer \(n\) such that both \(\operatorname{Im}w^n=0\) and \(\operatorname{Re}w^n>0\). [1]