Activated STATs can induce the expression of SOCS proteins, which in turn inhibit the JAK-dependent phosphorylation of the STATs. Under sustained serum stimulation of mouse fibroblast cells, a number of oscillations can be observed as a consequence of this delayed negative feedback loop, as shown in the following simplified graph. According to this graph, approximately how long is the delay in the feedback response, and what process is mainly responsible for it?