In this problem, you will practice using string manipulation in r studio, with a focus on the use of regular exxpressions $-$ the mini language for efficiently specifying string patterns. In the following sentence, extract all plural nouns, todo $<-$ "Yesterday, I needed to buy four cups of flour, a piece of Parmesean cheese, two gallons of ice cream, and a six$-$pack of bottled $($non$-$alcoholic$)$ beers."