$3.(25$ pts$.)$ A $1$ kH plane wave in water of $50$ Pa effective $($rms$)$ pressure is incident normally on the water$-$air boundary. $($a$)$ What is the effective pressure of the plane wave transmitted into the air? $($b$)$ What is the intensity of the incident wave in the water and of the wave transmitted into the air? $($c$)$ Express, as a decibel reduction, the ratio of the intensity of the transmitted wave in air to that of the incident wave in water. $($d$)$ Answer the same three questions for the above sound wave incident on a thick layer of ice. $($e$)$ What is the power reflection coefficient from the layer of ice?