At a concert, the number of security guards needed is based on the average density of people in an area of 25' x 25'called a block. the concert space measures 350' by 200'. the number of security guards is based on a number of blocks necessary and each security guard can only be responsible for one block. 12,000 people are expected to attend the concert. how many security guards will be needed? how many people, rounded to the nearest 10, will be in each block?