If a variable shouldn't change its value, we'll need to create it with the val keyword. Immutable values help in making code fool-proof.

Can you figure out how to declare each variable?

Nice! Because we're changing the value of peopleSaved, it has to be a var type. birthYear isn't something that would change, so it's of type val.

Oh noes! Since we're changing the value of peopleSaved at the end, wouldn't it make sense to create it with the var keyword?