$1.$ Given a vector x:

x $<-$ c$(4,6,5,7,10,9,4,15)$

What R command could I use to find out the sum of entries in X that are less than $7?2.$ Complete the following R command to generate the vector $(0,0\mathrm{.}5,1\mathrm{.}0,1\mathrm{.}5,2\mathrm{.}0,2\mathrm{.}5,3\mathrm{.}0)$

x $<-$ s$\_\_\_\_\_\_.3.$ What function must be used to make R scripts $($not console commands$)$ produce output? $4.$ A categorical variable with a fixed number of levels is a $\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_.?$