Total cost is 3,900. 115 x 20 = 2,300.
80 x 20 = 1,600. 2,300 + 1,600 = 3,900.
The answer should be 3.5 (sorry if i'm wrong) You list the numbers from lowest to highest and then subtract the third quartile from the first quartile.
Integer, because 5,901 is a whole number. Integers = Whole numbers with no decimals(which in this case, yes, it has no decimal)