In our widget example, we will assume that the fixed cost for the stapler, pen, and âfactoryâ is $10 and the cost of each worker hired is $5 per worker. Since fixed costs are constant, the firm incurs $10 regardless of the level of output. Labor is the only variable cost computed by $5 times the number of workers.
How Bull Sharks Can Live in Both Ocean and Fresh Water. Although there are a handful of species that live in freshwater, we tend to think of sharks as being ocean dwellers. But there is also a very unique shark that can live in both ocean and fresh water estuaries and lakes: the Bull Shark.
Now, thanks to the work of Chris and Gwen Lowe, we know that it is possible. 1  Unless they, like this Bull Shark (Carcharhinus leucas) photographed in the Bahamas, enter extremely shallow water, most sharks do not swim with their dorsal fins projecting above the surface.