Walter owns 60 books now. he plans to buy 10 books every month. which recursive formula gives the number of books walter will have in any month in the future?
a.) next = now + 10, starting at 60
b.) next = 60 × now + 10
c.) next = now + 60, starting at 60
d.) next = now + 10, starting at 10
e.) next = now × 10, starting at 60