Only thing I can tell you is to use a corner to a piece of paper. The corner is 90 degrees. It's acute if the corner is bigger than the angle. Obtuse if its smaller.
Answer:
4^2 = 16 16/3=5.333 but it should be 16 . if I am wrong so sorry ❤ don't hate me
First take the inside diameter and divide by 2 to get the radius (4cm)
Then use

r^2 with 'r' being your radius to get the area of the base
The area is 12.7 cm
Now multiply the height by the area of the base to get the volume/ capacity!
40cm x 12.7cm (rounded to the nearest tenth) = 502.7 cubic centimeters