Need help writing code in RStudio

data=coasters

variables=Name, Park, City, State, Country, Construction(Steel or Wood), Speed(km per hour), Height(meters), Length(meters), Inversions(Yes or No), Numinversions, Duration (seconds),GForce,Opened, Region.

1A. Change the units of the Speed variable to miles per hour rather than km per hour. (1 km per hour is equal to 0.6214 mph)

1B. How many rollercoasters are wood and how many roller coasters are steel. Write code that computes the number of each.