input: Write a function to compute the area of a circle given a radius as input. If the given radius is negative, return 0. Otherwise, return the area rounded to 2 decimal places.
  assert area_circle(5)==78.54
  assert area_circle(0)==0.00
  assert area_circle(-3)==0
output: def area_circle(radius):
      if radius < 0:
          return 0
      return round(3.14159 * radius * radius, 2)