Your friend tries to evaluate the idea of installing solar roof and asks for your advice. The initial costs including materials and installation are estimated to be $$18,000.$ It will generate enough electricity for the entire household for the next $30$ years. The monthly maintenance costs about $$10$ for the solar roof. Without the solar roof, your friend pays about $$150$ on electricity bill every month. Assume the annual cost of $8\%.$ What is the equivalent monthly cost for solar roof? What is the monthly saving or additional cost if going with solar $?$ What would you suggest $?$