$($Lecture $10)$: Evaluate two flood prevention projects using benefit$-$cost ratio: Project A has a cost of $$8$ million with annual benefits of $$1\mathrm{.}6$ million, and Project B has a cost of $$10$ million with annual benefits of $$2\mathrm{.}1$ million. Assume a $5\%$ interest rate. $(30$ Points$)$

Hint:

Assume an infinite life

$(\frac{A}{P},i\%,)=i\%$

The lowest cost option is

B$-$C lowest cost option