Answer:
Option B
Step-by-step explanation:
we know that
The sum of an arithmetic series is equal to
S=n(a1+an)/2
where
a1 is the first term
an is the last term
n is the number of terms
In this problem we have
n=20
a1=102
an=159
substitute the values in the formula
S=20(102+159)/2
84 feet
take the 7 yards into feel that is 21
times that buy 4 feet and you get 84 feet
