Draw a level 0 data flow diagram (DFD) for the process of buying glasses. The first step is to see an eye doctor who will give you a prescription. Patient information will be stored at doctor's office. Once you have a prescription, you go to a glass store, where you select your frames and place the order for your glasses. The glass store maintains information on frames and orders. Once the glasses have been made, you return to the store for a fitting and pay for glasses. The payment information is recorder in the order. You can use any tool to draw the diagram.