Final answer:
To calculate the amount of pesticide needed for a 20-acre application, we need to determine the total amount of pesticide needed per acre for each material and multiply it by 20 for 20 acres. The correct answer is option b. 10 gallons of Lancer and 20 lbs. of Doubt.
Step-by-step explanation:
To calculate the amount of pesticide needed for a 20-acre application, we need to first determine the total amount of pesticide needed per acre for each material. Lancer 2E is applied at a rate of 1 lb. active ingredient per acre, so for 20 acres, we would need 20 lbs. of Lancer 2E. Doubt 25DF is applied at a rate of 0.25 lb. active ingredient per acre, so for 20 acres, we would need 5 lbs. of Doubt 25DF. Therefore, the correct answer is option b. 10 gallons of Lancer and 20 lbs. of Doubt.