Let $A = f(r)$ be the area of a circle of radius $r$.

(a) Write a formula for $f(r) =$ help (formulas)

(b) Which expression represents the area of a circle whose radius is increased by 10%?

A. $f(1.1 r)$
B. $f(r+0.1)$
C. $f(r) + 0.1$
D. $f(10+r)$
E. $0.1 f(r)$

(c) By what percent does the area increase if the radius is increased by 10%?
% (round to the nearest 0.01%) help (numbers)