PL HELP ME IN THS

Question

Before building a triangular pen for his pigs, Jared drew a scale model on a piece of paper shown below. Jared already built a 10 ft. fence to correspond to side AB in the scale drawing. How many feet of fencing does he need to purchase to complete the pig pen? 

20 ft. of fencing 

21 ft. of fencing 

30 ft. of fencing 

31 ft. of

Answer 1

IF it's an equilateral triangle with all sides equal, then he needs 20 feet more and A is correct

But if the other two sides are longer, then one of B, C or D would be correct.