5. 7.25 Conventional and solar alternatives are available for providing energy at a remote radar site. Use the B/C ratio to determine which method should be selected at an interest rate of 8% per year and a 5- year study period. Table Summary: Table divided into three columns compares two energy-providing methods based on their rate of interest and time period. The column headers are marked from left to right as: method; conventional; and solar. Method Conventional Solar Initial cost, $ 300,000 2,500,000 Method Conventional Solar Annual cost, $ per year 700,000 5,000 6.