After working for 25 years as personal fitness trainers while raising their​ kids, three sisters cashed in a total of ​$80 comma 000 in bonds and decided to open a​ small, neighborhood fitness center. they spent the ​$80 comma 000 on exercise​ equipment, advertising, computer​ equipment, and other furnishings for the business. for the next 3​ years, they took in ​$150 comma 000 in revenue each​ year, paid themselves ​$35 comma 000 annually​ each, and rented a space in a strip mall for ​$22 comma 000 per year. before the​ investment, their ​$80 comma 000 in bonds were earning interest at a rate of 15 percent. are they now earning economic​ profits? explain​ your answer.

Feedback systems do not always involve negative feedback. economic inflation, which is evidenced by continually rising prices, is a positive feedback system. a positive feedback control system, as shown on the right, adds the feedback signal to the input signal, and the resulting signal is used as the input to the process. a simple model of the price-wage inflationary spiral is shown on the right. add additional feedback loops, such as legislative control or control of the tax rate, to stabilize the system. it is assumed that an increase in workers’ salaries, after some time delay, results an increase in prices. under what conditions could prices be stabilized by falsifying or delaying the availability of cost-ofliving data? how would a national wage and price economic guideline program affect the feedback system?