Answer:
The surface area is 3140 feet².
What is Surface Area?
Surface area is the amount of space covering the outside of a three-dimensional shape.
Given that:
Diameter = 20 feet
radius = 20 ÷ 2 = 10 feet
Now, Surface area will be,
=2πr²+ 2πrh
= 2 × 3.14 × (10)² + 2 × 3.14 × 10 × 40
= 6.28 × 100 + 6.28 × 400
= 628 + 25.12 × 100
= 628+ 2512
= 3140 feet²
hence, the surface area is 3140 feet².
Step-by-step explanation:
There are 6 other positions in the string, each with 26 choices. So if you fix BO as the first two letters, there are

possible strings that you can make.
If BO is at the end of the string, you still have

possible strings.
Together, then, you have

possible strings.