Помогите решить пару заданий.

Steven______________(work) at this problem for three months. We’ll be able to see the presentation next week. 4. We________________(just / buy) a new car. We can go to the see. 5. Before Olga came to London, she___________________(learn) English for three years. 6. When her mother came home, Helen____________________(clean) the room since morning. 7. Thank you for_______________(come) in time. 8. There is no reason in______________(argue). 9. If the train _________________(come) in time, we would not have been late at the concert. 10. Yesterday at 5 o’clock Tom _______________(do) his homework and could not go for a walk. 11. Yesterday by 5 o’clock Tom_______________(do) his homework and could go for a walk. 12. If you ________________(phone) me, I would go to the cinema. 13. When her mother came home, she______________(write) the letter and___________(go) to the park with her friends. 14. If he _______________( buy) a car, we’ll go to the see. 15. If he___________________(buy) a car, we would go to the see. 16. If he____________________(buy)a car , we would have gone to the see. 17. My father _________________(work) here for three years. 18. My father__________________( repair) this car since morning. 19. If I had learned the grammar rules, I __________________(not /get) a bad mark. 20. If I learned the grammar rules, I_______________________(not/ get) a bad mark. 21. If I learn the grammar rules, I_______________________( not / get) a bad mark.