I Was Caught at the Beginning and Asked Me If I Could Build an Electromagnetic Gun?

Yun Chen traveled through the parallel world and became a student at the University of Information Technology. The first thing he did when he traveled through time was to wash his hands happily! Just when Yun Chen was feeling happy, a group of armed police with guns and live ammunition rushed into the room. "We suspect you are selling arms, come with us!" In the interrogation room, the confused Yun Chen looked confused. "Is it illegal for me to just sell a piece of farm machinery?" Police: "Farm machinery?" "Did you know that the gas cans you sell are used as mortars in the Middle East!" "Did you know that the steel pipe you added a smooth bore to was used to make a rocket launcher?" "Do you know that your improved artificial rain bombs are used by others as intercontinental missiles?" "Do you know that the tracks of your improved tractor were removed and installed on the tank?" "Did you know that the speed of your improved drone has reached Mach 1?" "Is this a drone or a fighter jet?" "Now you tell me that you sell agricultural machinery?" "Last question, can the electromagnetic gun be modified?" Yun Chen: "Yes, but you need to bring your own materials and the price will be calculated separately!" One month later. "I asked you to make a sample. What did you make?" "With a range of three hundred kilometers, you said it's a sample?" ...