Question about the area of container

The input [1,1] means the top points are (1,1) and (2,1). Each point has a line travelling down to the xaxis, meaning the lines are ((1,1),(1,0)) and ((2,1),(2,0)). The question then asks what the maximum area of the container is, when the container's sides are the lines. There are only two lines from the input, so the sides are those two. The yaxis cannot be used as another line.
The area is the width times the height.
Width = P2.x  P1.x = 2  1 = 1
Height = min(P1.y, P2.y) = min(1,1) = 1
A = W*H = 1*1 = 1