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)