Answer: 16 square feet
Step-by-step explanation: In order to calculate how much total screen she needs you need to calculate each section.
The small ends are 2 ft x 1 ft, so you need 2 feet for each end, or 4 feet total.
The long sides are 3 ft x 2 ft, so you need 6 feet for each end, or 12 feet total.
The total screen needed for the sides is 4 + 12 = 16 square feet.