text: # Consider a child waiting at a street corner for a gap in traffic that is large enough so that he can safely cross the street.
  # A mathematical model for traffic shows that if the expected waiting time for the child is to be at most 1​ minute, then the maximum traffic​ flow, in cars per​ hour, is given by
  # f(x) = 29,403( 2.335 - log( x ) ) / x, where x is the width of the street in feet.
  
  from sympy import *
  
  init_printing()
  
  def disp_fun( f ):
  	pprint( '\n{0}\n\n'.format( pretty( f ) ) )
  
  x = symbols( 'x' )
  
  fX = 29403 * ( 2.335 - log( x, 10 ) )  / x
  dX = diff( fX, x )
  
  simplify( dX )
  
  # Find the maximum traffic flow and the rate of change of the maximum traffic flow with respect to street width for the street width of 35 feet.
  # (Do not round until the final answer. Then round to the nearest integer as​ needed.)
  round( fX.subs( { x: 35 } ).evalf(), 0 )
  
  # The rate of change of the maximum traffic flow is about X vehicles per hour per foot.
  # ​(Do not round until the final answer. Then round to the nearest tenth as​ needed.)
  round( dX.subs( { x: 35 } ).evalf(), 1 )
  
  
  # Find the maximum traffic flow and the rate of change of the maximum traffic flow with respect to street width for the street width of 54 feet.
  # (Do not round until the final answer. Then round to the nearest integer as​ needed.)
  round( fX.subs( { x: 54 } ).evalf(), 0 )
  
  # The rate of change of the maximum traffic flow is about X vehicles per hour per foot.
  # ​(Do not round until the final answer. Then round to the nearest tenth as​ needed.)
  round( dX.subs( { x: 54 } ).evalf(), 1 )