Read the following passage.The microwave oven is one of the most common household appliances in the world. But most people are unaware it owes its existence to a lucky accident. Percy Spencer, its American inventor, was a self-taught engineer working for an industrial corporation called Raytheon. In 1945 he was tasked with improving radar technology to aid the Allied forces' offensive during World War II.  Percy was in the lab testing magnetrons on that fateful day in early 1946. Magnetrons are high/-powered vacuum tubes used in radars. He had just walked past one of the magnetrons when he realised that a peanut cluster bar in his pocket had melted. A sudden curiosity gripped him to investigate this further.  He asked a disbelieving engineer to stand with an egg in front of the tubes. A few seconds later, it exploded in his face.   Percy treated the entire office the next day to popcorn popped by the magnetron. Armed with the knowledge of how to cook food in mere seconds, Percy patented the invention. In 1947 with the help of Raytheon, he perfected the first microwave oven called the Rada Range. It weighed almost 340 kilos, stood six feet tall and was priced at a whopping 5000 dollars. It took almost 20 minutes to warm up but was approximately ten times more powerful than today's microwaves. It could cook a potato in under half a minute. It turned out to be a commercial failure due to its steep price and poor marketing. However, microwaves shrank in size and price as the years progressed and were soon outselling gas ranges. Why did Percy patent his invention?