the length of arc ACB is 4 ft
Step-by-step explanation
the length of an arc is given by:

where l is the length or the arc, theta is the angle in degrees, r is the radius
so
Step 1
find the radius of the circle

Step 2
now, replace in the formula
Let
angle= 40 °

therefore, the length of arc ACB is 4 ft
I hope this helps you