a and b together can do a work in 10 days B and C together can do the same work in 15 days a b and c together can do the same work in 8 days then how many days can B alone do this work​

Two farmers pay a total rent of $140 for a pasture. the first farmer placed $4 oxen in the pasture, and the second farmer placed $30 sheep in the pasture. the farmers split the rent based on the proportion of the pasture eaten by their own animals that month. how much should the first farmer pay, if 1 ox eats as much as 10 sheep in a month?