Before purchasing videoconferencing$$ equipment, a company tested its current internal computer network. The tests measured how rapidly data moved through its network given the current demand on the network. Eighty files ranging in size from $20$ to $100$ megabytes$($MB$)$ were transmitted over the network at various times of$$ day, and the time to send the files$($in seconds$)$ recorded. In the accompanying$$ data, the time is given as the number of hours past $8$ A$.$M$.$ on the day of the test. Use the transfer time as the$$ response, with the file size and time of day as explanatory variables. Complete parts$($a$)$ through$($f$)$ below.