Zelda Industries is the only firm of its kind in the world. Due largely to historical accident, it began producing streganomas in 1985 in a vacant warehouse. Virtually anyone with a degree in college chemistry could easily replicate the firm's formula, which is not patent protected. Nonetheless, since 1985 Zelda has averaged accounting profits of 6 percent on investment. This rate is comparable to the average interest rate that large banks paid on deposits over the period. Do you think Zelda is earning monopoly profits? Why?