Janine is considering buying a water filter and a reusable water bottle rather than buying bottled water. Will doing so save her money? How much water does Jainine drink in a day? She normally drinks 3 bottles a day, each 16.9 ounces. How much does a bottle of water cost? She buys 24-packs of 16.9 ounces for $ 3.09. How much does a reusable water bottle last? Basically forever (or until you loose it). How much does a water filter cost? How much water will they filter? A faucet-mounted filter costs about $ 28 and includes one filter cartridge. Refill filters cost about $ 33 for a 3-pack. The box says each filter will filter up to 100 gallons (378 liters). A water filter pitcher costs about $ 22 and includes one filter cartridge. Refill filters cost about $ 20 for a 4-pack. The box says each filter lasts for 40 gallons or 4 months. An under-sink filter costs $ 130 and includes one filter cartridge. Refill filters cost about $ 60 each. The filter lasts for 500 gallons. Which option is the cheapest over one year (365 days)? Ans= faucet-mount filter. The cheapest option saves her $ ? Over a year? "I know that the answer is the Faucet-mount filter but I don't know how to do the math for how much she saves over a year.