Three processes are under consideration for producing drinking water from wastewater. The relevant economic information (in millions) is shown below. At an interest rate of 8% per year, the incremental B/C ratio between processes A and B is closest to:

Process A B Initial cost, $ 15 25 Annual cost, $/yr 4 4.5 Benefits, $/yr 6 7 Life, years 10 20 30 3.5 7.5 20 D 46 3.0 8 20 Less than 1 1.25 1.75 Over 1.9 MacBook Air