Detailed Instructions: The task is to generate the correct answer for a given math problem.
Problem:Problem: the points a ( 0 , 0 ) , b ( 0 , 4 a - 5 ) and c ( 2 a + 1 , 2 a + 5 ) form a triangle . if angle abc = 90 , what is the area of triangle abc ?
Solution:
82.5