Edit the following paragraph by adding commas where they are needed and removing unnecessary commas.

Exercise 32-c Commas and unnecessary commas (Editing paragraphs) To read about this topic, see the sections on the comma in your handbook. Edit the following paragraph by adding commas where they are needed and removing unnecessary commas. The first revision has been done for you. The first true clocks were built in the thirteenth century, an era when accurate timekeeping became increasingly important. There were some existing timekeeping devices such as, sundials. However these were often used in situations, that were not ideal. Sundials were useless at night, when there was insufficient light for casting a shadow. The wind could blow out candles which also could be used to estimate the time. The timekeeping devices, that used streams, could freeze in winter. By the thirteenth century the European monastery was a major social organization, that depended on precise accurate and reliable timing. The monks' cooperative work efforts required them to coordinate their duties, in terms of timing. This was an important need that called for a machine that could keep reliable time. Because of this the modern clock was devised