When you own a pet, there are one-time costs, such as a leash, and continuing costs, such as food. Suppose the one-time costs for owning a small dog are $180, and the continuing costs are $400 per yearWhich function models the average annual cost of owning a small dog for x years?f(x) = x/(180 + 400x)f(x) = x/(180x + 400)✔ f(x) = (180 + 400x)/xf(x) =(180x + 400)/x