When Henrietta Homeowner invests $100 to replace her old mechanical thermostat along with a new computerized “smart” thermostat, in that case her gas and electric bills will be decreased by $100 yearly all times. The rate of return onto this investment is: (w) 50 percent. (x) 100 percent. (y) 200 percent. (z) 1000 percent.
How can I solve my Economics problem? Please suggest me the correct answer.