The function f(x) = xπ−−√ gives the diameter, in inches, of a proposed spherical sculpture with a surface area of x square inches. The artist making the sculpture wants to know how the diameter changes if the surface area is increased. What is the average rate of change for the function as the surface area changes from 12.6 in.2 to 28.3 in.2? Round your answer to the nearest hundredth of an inch.