Using R, plot the pdfs of the random variables defined in parts (a)–(e) below. Obtain an overlay plot of all five pdfs, also. (a) X has a standard normal distribution. Use this code:...

Using R, plot the pdfs of the random variables defined in parts (a)–(e) below. Obtain an overlay plot of all five pdfs, also. (a) X has a standard normal distribution. Use this code:                                     x=seq(-6,6,.001); plot(dnorm(x)~x). (b) X has a t-distribution with 1 degree of freedom. Use the code:                                    lines(dt(x,1)~x,lty=2). (c) X has a t-distribution with 5 degrees of freedom.                                     lines(dt(x,5)~x,lty=2).  (d) X has a t-distribution with 15 degrees of freedom.                                      lines(dt(x,15)~x,lty=2). (e) X has a t-distribution with 25 degrees of freedom.                                      lines(dt(x,25)~x,lty=2).