I am trying to implement a model of product sales diffusion and
substitution. The model considers three generations of some product that
are introduced at times T1, T2, and T3. Each subsequently introduced
product will compete with the previously released products for sales. The
model thus takes a different for three time intervals:
Period of the first generation product (between T1 and T2):
Period of the first generation product (between T1 and T2):
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