1. Complete (i.e., copy into your code and them modify) the following if
   statement so that if age_class is equal to “sapling” it sets y <- 10.
age_class = "sapling"
if (){
  
}
y
2. Complete the following if statement so that if age_class is equal to
   “sapling” it sets y <- 10 and if age_class is equal to “seedling” it
   sets y <- 5.
age_class = "seedling"
if (){
  
}
y
3. Complete the following if statement so that if age_class is equal to
   “sapling” it sets y <- 10 and if age_class is equal to “seedling” it
   sets y <- 5 and if age_class is something else then it sets the value of
   y <- 0.
age_class = "adult"
if (){
  
}
y
4. Convert your conditional statement from (3) into a function that takes
   age_class as an argument and returns y. Call this function 5 times, once
   with each of the following values for age_class: “sapling”, “seedling”,
   “adult”, “mature”, “established”.