Answer:
50% discount
Step-by-step explanation:
We have the formula
price = marginal cost*(E/(E + 1) )
We are given the following:
price per unit item = $10
elasticity of demand, E = -3 for coupon users
marginal cost MC = ?
Hence
10 = MC * (-3/(-3 + 1))
10 = MC * 1.5
MC = 10 / 1.5 = 6.67
So, the appropriate discount that can be given is
price - marginal cost = 10 - 6.67 = $3.33 per box
OR 3.33 / 6.67 = 50% discount over cost.