please explain how one gets the answer

ucking company determined that the distance traveled per truck per year is normally distributed, with a mean of 60 is and miles and a standard deviation of 11 thousand miles. Complete parts (a) through (d) below. what proportion of trucks can be expected to travel between 47 and 60 thousand miles in a year? proportion of trucks that can be expected to travel between 47 and 60 thousand miles in a year is and to four decimal places as needed.) hat percentage of trucks can be expected to travel either less than 45 or more than BO thousand miles in a year? percentage of trucks that can be expected to travel either less than 45 or more than 80 thousand miles in a year is ad to two decimal places as needed.) many miles will be traveled by at least 90% of the trucks? umber of miles that will be traveled by at least 90% of the trucks is miles to the nearest mile as needed.) it are your answers to parts (a) through (c) if the standard deviation is 7 thousand miles? andard deviation is 7 thousand miles, the proportion of trucks that can be expected to travel between 47 and 60 ad miles in a year is to four decimal places as needed.) indard deviation is 7 thousand miles, the percentage of trucks that can be expected to travel either less than 45 or an 80 thousand miles in a year is %. to two decimal places as needed.) ndard deviation is 7 thousand miles, the number of miles that will be traveled by at least 90% of the trucks is miles. o the nearest mile as needed.) mean :400 47-40 LZ2 40-70 Stard = 11 1I - 13 4 2 2 2 ) = 1. 18 LZLO P (240) - P(2 2 - 1.18 )