3. Search for an R function that solves the roots of polynomial equations. (a) Find all roots of the following equation and save it as roots. (b) What is the mode of roots? (c) Use a single line command to sort the values in roots by ascending order of its imaginary part. (Note: the imaginary part of a complex number a +bi is b, where i -1. You can read the help document of the sort function by entering help (sort).)