Electromagnetic Waves

An electromagnetic wave, whose wave normal makes an angle of \(45^{\circ}\) with the vertical, travelling in air strikes a horizontal liquid surface. While travelling through the liquid it gets deviated through \(15^{\circ}\). What is the speed of the electromagnetic wave in the liquid, if the speed of electromagnetic wave in air is \(3 \times 10^8 \mathrm{~m} / \mathrm{s}\) ? \(\left(\sin 30^{\circ}=0.5, \sin 45^{\circ}=\frac{1}{\sqrt{2}}\right)\)