Simba travel agency arranges trips for climbing mount kilimanjaro. for each trip, they charge an initial fee of $100 dollars, in addition to a constant fee for each vertical meter climbed. for instance, the price for climbing to the shira volcanic cone, which is 3000 meters above the base of the mountain, is $400 dollars. let f(d) denote the fee of a trip f (measured in dollars) as a function of the vertical distance climbed d (measured in meters). write the function's formula.