The factory manufactures bicycles at the rate of 110+0.2t^2?0.7t bicycles per week (t in weeks). How many bicycles were made from day 8 to 28? Notice that t variable in the problem stands for the number of weeks. So, when we do the integral "from a to b", we will require those to be t values, or weeks. Which week starts on day 8? Similarly, which week ends on day 28?