A farmer has to transport 20 people and 32 sheep to a market. He can either use faits(x) which take 2 people and one sheep , or rolls Royce(y) which take two people and four sheep. He must not use mor

A farmer has to transport 20 people and 32 sheep to a market. He can either use faits(x) which take 2 people and one sheep , or rolls Royce(y) which take two people and four sheep.

He must not use more than fifteen cars altogether.

a. What is the lowest total number of cars he could use.

b. If it cost £ ten to hire each fait and £ thirty for each rolls Royce, what is the cheapest solution?