A thin layer of oil (\(n_{\text{oil}} = 1.50\)) floats on top of water (\(n_{\text{water}} = 1.33\)). Light with wavelength \(\lambda = 600\text{ nm}\) in air (\(n_{\text{air}} = 1.00\)) is incident nearly perpendicular to the oil film. Ray 1 reflects from the top surface of the oil film, while Ray 2 reflects from the bottom surface at the oil-water boundary, as shown in the diagram. What is the phase shift of Ray 2 upon reflection at the oil-water boundary, and what is the minimum non-zero film thickness \(t\) required for Ray 1 and Ray 2 to interfere constructively?