Consider the task of drawing the markings on a ruler: there is a mark at the halfway point, slightly shorter marks at the quarter intervals and still shorter marks at the eighth intervals. If our desired precision is $\frac{1}{2^n}$(arbitrary units), we put a mark at every point between $0$and $2^n$. The middle mark should be $n$units high the quarter marks should be $n-1$high, etc. Assuming we have a functionmark(x, h)to make a mark $h$units high at position $x$, the following program does the job of marking a ruler:

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defrule(left,right,height):ifheight>0:x=(left+right)/2mark(x,height)rule(left,x,height-1)rule(x,right,height-1)else:pass

Sincerule(left, right, height)is recursive we know that it will call itself. Suppose that we callrule(left=0, right=2**10, height=10). During recursive call number $9$torule(do not include the initial user call), it will make a mark at position $x$. What is the value of $x$?