The optimal mark$-$up is: $m=-\frac{1}{E+1}$ where $m$ is optimal mark$-$up and $E$ is the price elasticity of demand. When the mark$-$up on cookware equals $50\%($or $0\mathrm{.}5),$ then price elasticity of demand $($ E $)$ for cookware is:

$($Hint: Consider modeling this formula in Excel to answer this question correctly; and pay particular attention to the negative signs$)$

a$,-1$

b$.-1\mathrm{.}5$

C$.-2$

d$.-3$