Using the following information, what is the amount of gross profit? Purchases $36,000
Merchandise inventory, September 1 5,700
Selling expense 950
Merchandise inventory, September 30 7,400
Sales 95,000
Interest expense 1,340
Administrative expense 1,410
Rent revenue 1,700

Suppose an economist believes that the price level in the economy is directly related to the money supply, or the amount of money circulating in the economy. the economist proposes the following relationship: p=a x m - p=price level - m=money supply - a=a composite of other factors, including real gdp, that change very slowly over time. how might an economist gather empirical data to test the proposed relationship between money and the price level? an economist would persuade the federal reserve to change the money supply to various levels, and observe the resulting changes in the price level. unlike researchers in the hard sciences, economists cannot study complex relationships using data. economists do not usually develop theoretical models of the economy but only analyze summary statistics about the current state of the economy. an economist would look for data on past changes in the money supply, and note the resulting changes in the price level

Arival company manufactures fuel tanks for cars using a different production technique. the total weekly cost (in dollars) of producing x tanks is given by c(x) = 10000 +90x - 0.04x2 find the marginal cost at a production level of 500 fuel tanks per week to approximate the cost of the 501st unit (round to the nearest 2 decimal places, if needed)

Alarge tank is filled to capacity with 500 gallons of pure water. brine containing 2 pounds of salt per gallon is pumped into the tank at a rate of 5 gal/min. the well-mixed solution is pumped out at the same rate. find the number a(t) of pounds of salt in the tank at time t.