As a sound wave travels from liquid water into ice, its wavelength would
a) decrease due to wave speed decreasing as it passes through the ice.
b) increase because the wave speed and frequency have increased.
c) decrease since the frequency is now lower.
d) increase in order to keep the frequency the same due to the increase in speed.

Air is to be preheated by hot exhaust gases in a cross-flow heat exchanger before it enters the furnace. air enters the heat exchanger at 95 kpa and 20°c at a rate of 0.6 m^3/s. the combustion gases (cp = 1.10 kj/kg°c) enter at 160°c at a rate of 0.95 kg/s and leave at 95°c. determine the rate of heat transfer to the air and its outlet temperature.