What is the price elasticity of demand at the optimal price/quantity combination (use the next lower price level as the second point in your calculation)?

I am having trouble determining what values I am using for the calculation for the question above. I believe I would use the midpoint formula for (P2-P1) / (P1+P2) /2 / (Q2-Q1) / Q2+Q1)/2, but I do not know which values I should use to calculate it. Below is all the information included, along with answers, up to this question:

Scenario 1

A cupcake store is located in a mall and is the only cupcake store in that mall.The demand schedule for cupcakes (per dozen) is given in the table below.If the marginal cost to produce a dozen cupcakes is $4 per unit, how many units should the firm produce?

The firm should produce 100 units since the MR ($4.50) would still exceed MC ($4.00). If the firm produces 160, MC will exceed MR.

Price Quantity Purchased

$12 3

$11 7

$10 12

$9 20

$8 35

$7 60

$6 100

$5 160

$4 250

What price should the cupcake store charge?

The store should charge $6 per unit based on the marginal revenue (MR). The revenue decreases once the price goes under $6 to where the marginal costs (MC) exceed the MR. This price is also where MR and MC are closest.

If the fixed cost for the firm is $100 per day, how much profit will the firm make in one day?

By charging $6 and producing 100 units, the store would make $100 profit in one day.

What is the price elasticity of demand at the optimal price/quantity combination (use the next lower price level a

the second point in your calculation)?