Question 1202839
<pre>
PRICE       HOW MANY         COST
 40          150
 40-1        150+5
 40-2*1      150+2*5
 40-3*1      150+3*5       (40-3*1)(150+3*5)
.
.
.
 40-n       150+5n        (40-n)(150+5n)
</pre>
One way to continue this way is to use n for how many $1 increases, and look at the
cost expression for finding the maximum revenue.   (Quadratic in n).