Answer: 125.6 unit^2
Step-by-step explanation:
1) The formula for the lateral area of a cylinder is:
Lateral area = 2 π * radius * height
That formula is developed from the fact that when you "open" the cylinder through a line on the lateral area and perpedicular to the bases of the cylinder, the resultant figure is a rectangle with length 2π * radius and width equal to the height of the cylinder.
2) Calculations:
Lateral area = 2 π * 4 * 5 = 40π ≈ 40 (3.14) = 125.6 units^2