Step-by-step explanation below
Answer:
10.21 feet.
Step-by-step explanation:
circumference of circle with diameter d is given by 
where r is the radius of the circle.
_____________________________
given
diameter = 6 1/2 = 13/2 feet
\thus, circumference of circle is calculated as following

Thus, circumference of given circle is 10.21 feet.
Area of trapezium= 1/2 × (a+b) × h
= 1/2 × (12 + 8) × 8
= 1/2 × 20 × 8
= 10 × 8
= 80 cm^3
Hope it helps you