If 8 men and 5 women can earn Rs. 3390 in 6 days, an 5 men and 7 women can earn Rs. 3600 in 8 days, then in how many days will 7 men and 8 women earn Rs. 6435?
1)9 days 2)11 days 3)12 days 4)13 days 5)15 days