Biologsts often construct a food network of species in an ecosystem. The vertices represent species, and a directed edge (u, v) means species u eats species v. Determine the effect of the extinction of a species. If a species v goes extinct, and there is some other species u that only eats v, then u will become extinct. This can cascade through the food network Given a food network and a species v, determine all other species that will become extinct if v goes extinct. Show pseudocode and work out the running time