7.11 An entrepreneurial mechanical engineer started a tire shredding business to take advantage of a Texas state law that out- laws the disposal of whole tires in sani- tary landfills. The cost of the shredder was $220,000. She spent $15,000 to get 460-volt power to the site and another $76,000 in site preparation. Through con- tracts with tire dealers, she was paid $2 per tire and handled an average of 12.000 tires per month for 3 years. The annual operat- ing costs for labor, power, repairs, etc., amounted to $1.05 per tire. She also sold some of the tire chips to septic tank in- stallers for use in drain fields. This en- deavor netted $2000 per month. After 3 years, she sold the equipment for $100,000. What rate of return did she make (a) per month and (b) per year (nominal and effective)