Simba Travel Agency arranges trips for climbing Mount Kilimanjaro. For each trip, they charge an initial fee of $100 in addition to a constant fee for each vertical meter climbed. For instance, the total fee for climbing to the Shira Volcanic Cone, which is 3000 meters above the base of the mountain, is $400. Let y represent the total fee (in dollars) of a trip where they climbed x vertical meters.
Complete the equation for the relationship between the total fee and vertical distance.