Dear Julia and Dave, 

     To Julia: First, you should keep a good bedtime and wake-time. Secondly, you shouldn't drink coffee,

tea or colas in the evening. Thirdly, don't eat or drink too much two hours before you go to bed. Lastly

(In the end), you'd better take enough exercise at the right time. Late afternoon exercise can help you fall

asleep at night.

     To Dave: You shouldn't sit for a long time at the computer. Please stand up and have a rest every hour.

Maybe you can take some exercise. You had better look out of window every twenty minutes and do eye

exercises every two hours. At last you need to get a comfortable chair and desk. Get well soon!

                                                                                                                                           Doctor

(答案不唯一)