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Consider a function f defined by f$($x$)=9-^2.$ We want to find the area of $$the surface bounded by the curve y $=$ f$($x$),$ the x axis and the lines x $=-2$ and x $=0.$

a$)$ Find algebraically the Riemann sum S$,$ obtained by cutting the surface into n intervals of equal width and considering the circumscribed rectangles

b$)$ Evaluate the area of $$this surface by finding lim S$.$

c$)$ Evaluate the area using the fundamental theorem of calculus $($exact answer$)$