A sinusoidal wave of wavelength \( 7.5 \, \text{cm} \) travels a distance of \( 1.2 \, \text{cm} \) along the \( x \)-direction in \( 0.3 \, \text{sec} \). The crest \( P \) is at \( x = 0 \) at \( t = 0 \, \text{sec} \) and maximum displacement of the wave is \( 2 \, \text{cm} \). Which equation correctly represents this wave?