from typing import List


def _trapezoid_area(point_left: List[float], point_right: List[float]) -> float:
  """Computes the area under the line between the given control points.

  Args:
    point_left: ([x, y]) The upper left corner of the trapesoid.
    point_right: ([x, y]) The upper right corner of the trapesoid.

  Returns:
    The area of the trapesoid.
  """
  left_x, left_y = point_left
  right_x, right_y = point_right
  base = abs(right_x - left_x)
  height = (left_y + right_y) / 2.
  return base * height