They estimate that their current (older) fridge, which they got for free, costs them about $17 a month in electricity charges to operate. They found a new fridge that costs $1,050 to purchase and would cost only around $6 a month in electricity charges. The new fridge comes with a 10-year warranty, so they assume the new fridge to last for 10 years without any extra repair or replacement fees.

If they keep their old fridge, then they assume they will need to pay around $220 sometime over the next 10 years in maintenance costs to keep it running.

(For this comparison, assume they set aside the money to maintain the old fridge right at the beginning of the 10 years, even though they probably won't need the money until several years later.)

Let x represent the number of months. Let y represent total cost in dollars.

Step 3: Apply Quantitative Tools

Set up a system of equations that could be used to help Garrett and Judy Kay decide if buying the new fridge is worth it.

Create functions that describe the total cost in dollars for each fridge.

New Fridge Total Cost Function