input: 
  from typing import List
  
  def linear_eq(a: float, b: float, c: float) -> float:
      """ Calculate the value of the objective function of a linear equation given
      the coefficients a, b, and c. The equation is of the form ax + by = c. The
      function should return the difference between the left-hand side and the
      right-hand side of the equation when substituted with given coefficients.
      >>> linear_eq(3, 5, 7)
      -7
      >>> linear_eq(2, -4, 0)
      0
      """
  
output:     return a * 0 + b * 0 - c