The length of the straight portion of a bar beyond the end of the hook, should be at least_______________?

Given Answer is Correct.
According to R-AGOR EDITION 2006, CHAPTER No 13 QUESTION 13.31
Most of students are confused and thinking about 4 Times the dia. They are 100% correct but in case of “DEFORMED BARS & Mild Steel” that is mentioned in RS-KHURMI CHAPTER RCC STRUCTURE DESIGN QUESTION 82 also in R-AGOR QUESTION# 13.28
here some specifications are given in case of DEFORMED BARS & Mild Steel:
As per IS 456 (Clause 26.2.2.2).

1. When the bar is bent at an angle of at least 90 degree round a bar of at least own dia. and it continued beyond the end of the curve for length of at least eight diameters (8d).

2.when the bar is bent at an angle of 135 degree round a bar of at least own dia. and it continued beyond the end of the curve for the length of at least six diameters (6d). (HYSD High Yielding Strength Deformed on Radius )

3. when the bar is bent through an angle of 180 degree round a bar of at least own dia. and it continued beyond the end of the curve for the length of at least four diameters (4d).