please solve in clear and detailed baby steps

We want to transport 300ft3/min of air horizontally from our air conditioner to an outbuilding 800ft away. The air is at 40F and a pressure of 0.1psig. At the outbuilding the pressure is to be 0.0psig. We will use a circular sheet metal duct, which has a roughness of 0.00006 in. Find the required duct diameter: We can use the Figure in next slide to solve this problem without the complicated trial and error we used before