RRB NTPC CBT I 16 Jan 2021 Shift 1 Paper

There is a 6-storey building with 20 rooms on each floor. Some toxic material is concealed in the building. Three groups of officers start the search operation simultaneously. The first group searches the 1st and 2nd floors. The second group handles the 3rd and 4th floors. The third group takes over the 5th and 6th floors. If it takes 1 minute to reach any nearest floor and 1 minute to search each room, how much time will it take to complete the entire search operation?