Answer: (1) 700 pizzas
(2) Its revenue increases by $2600.
Step-by-step explanation:
Given that,
price elasticity of demand for his pizza = -4
Percentage change in price = 10%
Initial Quantity,
= 500 Pizzas
Elasticity of demand =
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-4 =

= -4 × 0.1
= 0.4
= 0.4
∴
= 700
Initial price,
= $20
Changed price,
= $18
Revenue at t = 0
= 500 × 20 =$10000
Revenue at t = 1
= 700 × 18 = $12600
Therefore, from the above calculations it was seen that his revenue increases by ($12600 - $10000)= $2600 and its sales increases to 700.