4. A farmer plans to produce 4 different crops in 5 different fields. The farmer's fields are 100, 70, 150, 80 and 90 acres respectively. Wheat, barley, cotton in the first field, wheat, barley, corn in the second field, wheat, barley in the third field, corn, cotton in the fourth field and all products in the fifth field. A product can be planted in a field, as well as more than one product. The products (in kilograms) that can be obtained per acre from the fields are given in the table below. Field 1 Field 2 Field 3 Field 4 Field 5 Wheat 400 500 450 300 350 400 350 Barley Corn 400 1100 1300 1200 Cotton 250 300 250 Per kilogram, it is estimated that a profit of 0.10 $ from wheat, 0.15 $ from barley, 0.15 $ from corn and 0.50 $ from cotton is expected. The farmer wants wheat for at least 30%, barley for 20%, corn for 10% and cotton for 20% of their total land. In addition, in order for it to be economical to plant a product in a field, at least 35, 25, 15, 30 decares should be planted for wheat, barley, corn and cotton, respectively. What kind of planting should the farmer make to maximize his profit? Write down the decision model. Find the best solution by writing the GAMS code of the problem. 4. A farmer plans to produce 4 different crops in 5 different fields. The farmer's fields are 100, 70, 150, 80 and 90 acres respectively. Wheat, barley, cotton in the first field, wheat, barley, corn in the second field, wheat, barley in the third field, corn, cotton in the fourth field and all products in the fifth field. A product can be planted in a field, as well as more than one product. The products (in kilograms) that can be obtained per acre from the fields are given in the table below. Field 1 Field 2 Field 3 Field 4 Field 5 Wheat 400 500 450 300 350 400 350 Barley Corn 400 1100 1300 1200 Cotton 250 300 250 Per kilogram, it is estimated that a profit of 0.10 $ from wheat, 0.15 $ from barley, 0.15 $ from corn and 0.50 $ from cotton is expected. The farmer wants wheat for at least 30%, barley for 20%, corn for 10% and cotton for 20% of their total land. In addition, in order for it to be economical to plant a product in a field, at least 35, 25, 15, 30 decares should be planted for wheat, barley, corn and cotton, respectively. What kind of planting should the farmer make to maximize his profit? Write down the decision model. Find the best solution by writing the GAMS code of the