Network Modeling the Quickest Route

"Northwest Travel Problem The travel times (hours) along various routes in the Pacific Northwest is shown below. Question 1: What is the quickest route from Seattle to Denver? Question 2: What is the quickest route from Portland to Cheyenne? Question 3: What is the quickest route from Seattle to Denver, if you are required to pass through both Butte and Salt Lake City along the way? Question 4: A snow storm has closed down I-90. With I-90 closed, what is the quickest alternate route from Seattle to Denver? "