This problem involves the probability-density function, , for the end-to-end length, , of the random-flights chain. Some useful expressions to help solve this problem are given on the facing page of this exam. The functions erf (x) and erfc (x) are special functions known as the error function and the error function complement, respectively. These special functions are tabulated in handbooks and their values can also be found on various internet sites. The mean value of is equal to , where is the number of random-flights segments and is the segment length. Using the information provided, find the probability that lies within the interval