Calculus: Early Transcendentals, Chapter 4, 4.6, Section 4.6, Problem 3

See the attached graph of f(image) in red color and links.Graph is drawn on two ranges for better clarity.
From the graph , f is decreasing on intervals (-oo ,-15) and (4.40,19.0)
f is increasing on intervals (-15,4.40) and (19,oo )
Local minimum f(-15) ~~ -9,687,500 f(19) ~~ -12,500,000
Local maximum f(4.4) ~~ 54,000
See the graph of f' in link blue color ,
graph of f'' in link green color
From the graph
Function is concave up on the intervals (-oo ,-11) , (0,3) and (15,oo )
Function is concave down on the intervals (-11,0) and (3,15)
Inflection points at x=0 , x ~~ -11 , 3 , -15