The probability density function for a normal distribution ("bell curve") with mean and variance 2 is given by f(x)=21e22(x)2,xR,R,2>0. (a) Write an R function called mdnorm1 that computes f(x) for any value of x, and . (b) Copy the function in (a) and call it mdnorm2. Set the defaults for and to be 0 and 1 respectively. (c) Copy the function in (b) and call it mdnorm3. Add a new input called log that defaults to FALSE. If FALSE return f(x) otherwise return lnf(x). Make sure you first simplify the expression returned when TRUE. Submit your R code as q3.R. Also, please label each part (a)-(c) with a comment like you did for question 1 )