Steel cable barriers in highway medians are a lowcost way to improve traffic safety without overstressing department of transportation budgets. Cable barriers cost $44,000 per mile, compared with $72,000 per mile for guardrail and $419,000 per mile for concrete barriers. Furthermore, cable barriers tend to snag tractor-trailer rigs, keeping them from ricocheting back into same-direction traffic. The state of Ohio spent $4.97 million installing 113 miles of cable barriers. Answer the following using both tabulated factors and a spreadsheet function.

(a) If the cable barriers prevent accidents totaling $1.3 million per year, what rate of return does this represent over a 10-year study period?

(b) What is the rate of return for 113 miles of guardrail if accident prevention is $1.1 million per year over a 10-year study period?