It's local maximum value will be at a place where the function g(x) just turns from positive slope to a negative slope, ie. g'(x)=0
The equation starts from the -∞ and rises till its slope gets zero for the first time, so the least value of x that satisfies g'(x) will provide the required result.
Roots of x=
Least value will be the one with the negative sign ie.
To find the area of this just add the units I believe which is 21 Hope this helps good luck. Not sure if this is 100% right my last year teacher was a sucky one