A drier requires \(1.5 \mathrm{~m}^{3} / \mathrm{s}\) of air at \(338 \mathrm{~K}, 1 \mathrm{~atm}\), and \(20 \%\) relative humidity. This is to be prepared from air at \(300 \mathrm{~K}\) dry-bulb, \(291 \mathrm{~K}\) wet-bulb temperatures by direct injection of steam into the airstream followed by passage of the air over steamheated finned tubes. The available steam is saturated at \(383 \mathrm{~K}\). Calculate the kilograms of steam per second required for

(a) direct injection and

(b) the heat exchanger. Assume that in the heat exchanger the steam condenses at constant temperature.