Break$-$even point: Changing costs$/$revenues JWG Company publishes Creative Crosswords. Last year, the book of puzzles sold for $$9\mathrm{.}49$ with variable operating cost per book of $$7\mathrm{.}02$ and fixed operating costs of $$40,000.$

a$.$ How many books must JWG sell this year to achieve the break$-$even point for the stated operating costs, if all figures remain the same as for last year?

b$.$ How many books must JWG sell this year to achieve the break$-$even point for the stated operating costs, if fixed operating costs increase to $$43,800$ and all other figures remain the same?

c$.$ How many books must JWG sell this year to achieve the break$-$even point for the stated operating costs, if the selling price increases to $$10\mathrm{.}13$ and all costs remain the same as for last year?

d$.$ How many books must JWG sell this year to achieve the break$-$even point for the stated operating costs, if the variable operating cost per book increases to $$7\mathrm{.}66$ and all other figures remain the same?

e$.$ What conclusions about the operating break$-$even point can be drawn from your answers?

a$.$ The break$-$even poing will be $$ books. $($Round to the nearest integer.$)$