3.: If f(13) is a positive continuous function on R , what does the function F(:1:) = ft) dt 0. represent (for a: > a) ? O The slope of the tangent line to the graph of f at a: . O The area of a rectangle with base on the horizontal axis. 0 The area between the graph of f and the x-axis on the interval [a , m] . O The average value of at) on the interval [a , as]