1. Work: Leaking flour

As a flour sack is being raised a distance of 9 feet, flour leaks out at such rate that the number of pounds lost is directly proportional to the square root of the distance traveled. If the sack originally contained 60 lb of flour and it loses a total of 12 lb while being raised the 9ft, find the work done in raising the sack.

So i have here
9 feet
no of pounds lost is directly proportional to 3 feet
60lb to 48lb while raising the 9 ft

I have no idea what to do the example on the book is very confusing

As a flour sack is being raised a distance of 9 feet, flour leaks out at such rate that the number of pounds lost is directly proportional to the square root of the distance traveled. If the sack originally contained 60 lb of flour and it loses a total of 12 lb while being raised the 9ft, find the work done in raising the sack.

So i have here
9 feet
no of pounds lost is directly proportional to 3 feet
60lb to 48lb while raising the 9 ft

I have no idea what to do the example on the book is very confusing
Using pound as a unit of mass; the work done is:

$
\int_0^9 m(x)g ~dx
$

and the next bit is confused but I think it means:

$
m(x)=60-k\sqrt{x}
$

with:

$
12=k \sqrt{9}
$

RonL