point price elasticity of demand

When P=$5 - $0.05Q, and Q =40, the point price elasticity of demand is: a. -2/3, b. -3/2, c. -8/3 d.-3/8. I know that when you plug 40 into the .05Q, you get 2, and 5-2=3, so I think the answer is b. but I can't figure out why. I would really appreciate an explanation. Thank you. Is this a slope, rise over run thing?

Point Price Elasticity

If P1 =$5, Q1 =10,000, P2=$6 and Q2=5000, then at point P2 the point price elasticity Ep equals: a. -6 b. -2.5 c. -4.25 d. -0/12

Econometrics

1. Given Equilibrium Price of A = $20 Price of B = $80 What is the Marginal Utility of product A divided by the Marginal Utility of product B? 2. Given: Total Revenue = $3000 Quantity Sold = 50 Quantity Produced = 75 What was the price? 3. Given: At $20 a hat 100 hats were sold. At $21 a hat 95 hats were sold. What is the elasticity of demand (using midpoint formula)? 4. Given: Total Cost = $1000 Average Variable Cost = $10 Quantity Produced = 50 What is the Total Fixed Cost? 5. Given The cross elasticity of demand between hotdogs and hamburger price = 0.5 What will be the percent change in hotdog sales if the price of hamburgers goes up by 10%?

Calculate total cost using Average Total Cost

I am supposed to use the following information to answer What is the total cost of 3,000,000 pairs I'm not sure if my answer is correct or not. 3,000,000 * $20.00 = $60,000,000 Is this correct? If not could you show your work so that I can understand how to do it? Athletic Shoe Production Normal Profit $6.00 Leather costs $2.00 Rubber costs $3.50 Metal costs $ .50 Cotton costs $3.00 Assembly $5.00 Total: $20.00 This is the lowest possible cost for the production of a single pair of shoes. It is also the Average total cost (ATC) of the profit maximizing or loss minimizing quantity of shoes: 3,000,000 Plant & Equ... click for more

Calculate Average Variable Cost using Average Total cost

Find average variable cost of 3,000,000 pairs of shoes Is the answer $16.00? I got that answer by multipling the ATC ($20.00) by the percent of variable cost (80%) Athletic Shoe Production Normal Profit $6.00 Leather costs $2.00 Rubber costs $3.50 Metal costs $ .50 Cotton costs $3.00 Assembly $5.00 Total: $20.00 This is the lowest possible cost for the production of a single pair of shoes. It is also the Average total cost (ATC) of the profit maximizing or loss minimizing quantity of shoes: 3,000,000 Plant & Equipment 20% if total assembly cost (not ATC) Labor 80% of total assembly cost (not ATC)