**Concept: **The question tests on the ability of framing and solving equations.

**Solution:**

Let us assume that the regular charges that John actually had was x dollars, Let the estimate of the time that he intended for this particular job = y hours,

=>x y =36

But however, there is a little bit of a change because the job took four hours longer.

So, its y+4 now and it no longer is x$ ,rather (x-2).

(x -2)(y+4)=336

=>(x-2) (y+4) = x y(Both equal 336)

=>x y + 4x -2y – 8 = x y

=> y = 2x-4 …….(1)

Now plug in the options (for y) and check where you get x y =336.

At Y=24 (option B) x= y+4/2(from 1) = 14

X y= 14 x 24 = 336 . Hence

**Option B.**