请你以"Why Not Ride a Bike?"为题,写一篇70词左右的英语短文.

As a commuter student,my favorite mode of transportation is bike.I prefer riding a bike to driving a car for several reasons.First and foremost,bikes are cheap,especially when you get them from second-hand stores.On average,a bike costs you no more than 50 dollars,which is way cheaper than a fancy car,not to mention that auto maintenance costs are extremely high and still rising.Second,bikes are small so they don’t take up much space.Instead of renting or purchasing a garage for your car,you can simply park your bike in your apartment.Last but not least,riding a bike is environmentally friendly.They don’t produce waste gases like cars,which can cause long-term damage to the environment and our health.In a nutshell,bikes are convenient,environmentally friendly,and economically feasible for most people.Why not ride a bike?

　　Why Not Ride a Bike?
　Dear David,
　You're still riding that bicycle you got from your 7th birthday. You've been riding it for 11 years now and your still riding it. Why not ride a bike? It's...