As we saw in Exercise 66 of Section 9.2, researchers have estimated the maximum life span (in years) for various species of mammals according to the formula L(E, P) = 23E^0.6P^-0.267, where E is the average brain mass and P is the average body mass (both in g). Consider humans, with E = 14,100 g and P = 68,700 g. Find the approximate change in life span if the brain mass increases to 14,300 g and the body mass decreases to 68,400 g. Then calculate the actual change in life span and compare.