4- Consider the following four design alternatives. Each design alternative has the same service life of 8 years and the MARR is 10% per year. The anticipated annual benefit, initial investment cost, and annual operating and maintaining cost are as follows. Which design would be the best alternative using the B/C ratio on incremental investment? B Initial investment cost, $ million Annual benefit, S million Annual O&M cost, $ million A 35.5 7.377 0.5 40.1 6.614 0.45 45.9 10.454 0.425 D 55.3 10.954 0.25