A factory in a rural area produces fermentation products with a capacity of $1000$ tonnes$/$yr$.$ The controlled emission factor for odor emissions averages $20000$ odor units $($OU$)$ per kilogram of products, and all emissions are released to the atmosphere through an elevated stack with an inner diameter of $0\mathrm{.}6$ m at the point of release. The stack height is $50$ m$.$ The flue gas is $15000$ Nm$3/$h$.$ The stack gas temperature is $40\backslash$deg C$.$

a$)$ Estimate the ground level odor concentration $500$ m south of the factory if the wind blows from north at a speed of $1\mathrm{.}5$ m$/$s on a sunny midday of July. Ambient temperature is $30\backslash$deg C$.$