A spool of total mass \(M\) consists of a central hub of radius \(r\) and two outer flanges of radius \(R\). The spool has a non-uniform mass distribution resulting in a rotational inertia \(I\) about its center of mass. A light string wrapped around the top of the central hub is pulled horizontally to the right with a constant force of magnitude \(T\), causing the spool to roll without slipping to the right along a horizontal surface. Which of the following correctly gives the magnitude of the linear acceleration \(a\) of the spool's center of mass, and the direction of the static friction force exerted on the spool by the surface if \(I > MRr\)?