1. A method for mixing models to optimize media placement, the method comprising: receiving a user input of a plurality of combinations of decision variables, wherein each of the plurality of combinations is associated with a potential media placement slot; retrieving a first subset of the plurality of combinations of decision variables; applying the retrieved first subset to a first linear model that represents a first relationship between the plurality of combinations and associated reach metrics to generate a first reach metric associated with the first subset; retrieving a second subset of the plurality of combinations of decision variables; applying the retrieved second subset to a second non-linear model that represents a second relationship between the plurality of combinations and associated reach metrics to generate a second reach metric associated with the second subset; comparing the first reach metric and the second reach metric; determining, based on the comparison, that the first reach metric is greater than the second reach metric; and storing, in a media placement database, an identifier of a media asset in a media placement slot associated with the plurality of combinations of decision variables in the first subset.