input: Write a function to evaluate a boolean expression given four boolean inputs.
  assert booleanExpression(True, False, True, False) == True
  assert booleanExpression(False, False, False, True) == True
  assert booleanExpression(True, True, False, False) == False
output: def booleanExpression(a, b, c, d):
      return (a or b) and (c or d)