Consider sending a large file

Consider sending a large file of F bits from Host A to Host B. There are two links(and one switch)between A and B, and the links are uncongested (that is, no queuing delays). Host A segments the file into segments of S bits each and adds 40 bits of header to each segment, forming packets of L=40+S bits Each link has a transmission rate of R bps Find the value of s that minimizes the delay of moving the file from Host A to Host B. Disregard propagation delay.