Answer:
total revenue  for 500 is $2500
total revenue  for 400 is $2800
Explanation:
given data 
price of good A = $50
quantity demanded of good A = 500 units
price of good A rises = $70
quantity demanded of good A falls = 400 units
solution
we get here Elasticity of demand that is express as
Elasticity of demand = (change in quantity ÷ average quantity) ÷ (change in price ÷ average price)   .......................1
here 
Change in quantity is = 400 - 500 = -100  
and average quantity is =   = 450
 = 450 
and change in price is = 70 - 50 = 20 
average price is =  = 60
 = 60
so now we put all value in equation 1 
Elasticity of demand  = 
Elasticity of demand  = -0.67 
as here the elasticity of demand is inelastic because elasticity is above -1
so about total revenue when price will increases as elasticity is inelastic
so increase in price will cause increase in revenue because revenue is maximum when elasticity = -1 
and increase in price will cause increases elasticity in the absolute term and revenue will increase
total revenue = price × quantity 
so 
total revenue  for 500 = 500 × 5 = $2500
total revenue  for 400 = 400 × 7 = $2800