Using functions from the package $`$dplyr$`,$ split the values in the column $`$Sub Category$`$ into the columns $`$Category$`$ and $`$Sub Category$`$ according to the following rules:

$1.$ Split the values based on the first occurrence of $`-`$

$2.$ When $`-`$ does not occur do not split the value. In this case simply use the original value as the $`$Category$`$ and set the $`$Sub Category$`$ as NA

$3.$ When there is more than one occurrence of $`-`,$ do not perform any additional splits.

Store your answer as the object $`$q$4`.$