MARR $=10\%.$ Which of the following mutually exclusive project alternatives should be approved? The service life of each project is $5$ years. None is an option.

Project A: First cost of $$1000.$ Annual savings of $$300.$

Project B: First cost of $$1200.$ Annual savings of $$400.$

Project C: First cost of $$1800.$ Annual Savings of $$450.$