Q$6$ The city of Manila is considering building a $10-$mile bike lane. The cost would be US $4\mathrm{.}5$ million and would take $1$ year to be completed. Once the project is built, the project will bring the following expected benefits: $*$reference graph.

a$)$ If the discount rate is $9\%,$ should the Manila build the bike lane?

b$)$ What if the discount rate were $10\%?$ Should the city build the bike lane?