A trucking company determined that the distance traveled per truck per year is normally distributed, with a mean of 30 thousand miles and a standard deviation of 12 thousand miles. Complete parts (a) through (c) below. a. What proportion of trucks can be expected to travel between 15 and 30 thousand miles in a year? The proportion of trucks that can be expected to travel between 15 and 30 thousand miles in a year is (Round to four decimal places as needed.)