Akshita and Raina are typing a book, but have only one laptop to work upon. They decided that they will work on alternate basis such that Akshita works for the first day, Raina works for the second day, Akshita for the third day and so on. Akshita alone can finish the typing work in 16 days, while Raina will take 24 days if she works alone on the entire book. How many days will they take to finish the typing work if they work on alternate basis?