Переделайте следующие предложения в Passive Voice. 
1. You must do three of these exercises tomor¬row. 2. You can find the book you need in any library. 3. We must send these letters at once. 4. You must take the box to the station. 5. You can cross the river on a raft. 6. The workers сan finish the building of the house very soon. 7. You must return the books the day after tomorrow. 8. I can easily forgive this mistake. 9. You can find such berries everywhere. 10. You must do this work very carefully. 11. The doctor says they must take her to hospital. 12. You can do the work in three days. 13. The students must return all the library books before each summer vacation. 14. Monkeys can climb even the tallest frees.