Question 187579
{{{d = 600 - 40p}}}
The more {{{p}}} increases, the smaller {{{d}}} becomes
(a) She will sell less if she raises the price
(b) Every time she raises the price $1, the 2nd term 
on the right increases by {{{40}}}, so {{{d}}} decreses
by {{{40}}}, so the nuber of cans she sells drops by {{{40}}}
{{{ graph( 500, 500, -3, 17, -50, 650, 600 - 40x) }}}
{{{d}}} is the vertical axis
{{{p}}} is the horizontal axis