Find the median:
1
8
4
30
39
16
33
18
7
5
11
13

12

Step-by-step explanation:

line the numbers up and cross off the first and last until you get to the middle. 11 and 13 were in the middle. 12 is between those numbers.

12

Step-by-step explanation:

1). Order the numbers from least to greatest

2). Elliminate one number from each side until you reach the middle

3). Since there are 2 numbers in the middle, we add the up (11+13) and divide them by 2

this is answer of 144 cubic meters