(8 pts) As we know, the back button (Go back one page) in our Browser relies on a stack to hold pages we visited previously, how about the forward button (Go forward one page)? Assume that we visited several pages according to the order shown below: pageA, pageB, pagee nageD, pageE Assume that we are at pggeD now. Please answer the questions below. 2.1. if we click the back button 2 times, then what page will be shown in our Browser? 2.2. after step 2.1, if we click the forward button, what page will be loaded? 2.3. after step 2.2, can we go to pageE? If yes, how many times we need to click the forward button? If no, explain. 2.4. based on your observation, what kind of data structure is appropriate for the forward button to hold page information