I just wanted to find out where I got lost. Please point out the point where I made the mistake.

Data Inc. produces price customization software calledBuy It. Based on an analysis of monthly product sales over a one-year period, Data Inc.'s marketing department estimates the demand forBuy Itto be:

Q_B= 1,200 - 8P_B+ 4P_S

Q_Bdenotes units sold ofBuy Itsoftware, P_BdenotesBuy It'sprice, and P_Sdenotes the price of a best-selling sales analytics software package (with both prices in dollars). The standard error of the estimate is 21.

a) Currently, P_B= $200 and P_S= $250. What is the predicted demand forBuy Itsoftware? (10 points)

b) An industry analyst comments that demand forBuy Itis not very sensitive to changes in the price of the statistical software package P_S. Carefully assess this contention. Do you agree or disagree? (20 points)

c) A marketing department analyst realizes that a potentially important determinant of demand forBuy Itsoftware is the price of computer workstations. The analyst reruns the regression model and now includes the price of workstations along with the other variables. What statistics would you like to have - and why - to evaluate the estimate? (20 points)

Can you walk me through? I had the answer follows;

Problem1:

a) Define the demand for Buy It software

given equation: Qb=1,200-8Pb+4Ps

Qb=1,200-8*(200)+4*(250)

Qb=1,200-1,600+1,000

Qb=600

A. Qb(demand for Buy It software) = 600units

b) Assess this contention

According to given equation, best-selling sales analytics software package elasticity is dQ/dP=+4

Input dQ/dP=4, P=200 and Q=600, into E=dQ/dP*(P/Q)

Ep=4*200/600

Ep=1.33

A. When the value ofelasticityisgreater than1.0, it suggests that thedemand is affected by the price. Therefore, the consumers are assumed to be price sensitive.

c) In order to undertake more analysis (i.e. maximize the profit ), we need to have more information about demand curve.

With the exception of the demand functions, the elasticity of price varies along the curve which means that we can't just use the Ep=1.33 to determine the optimal price as this value is only valid for a specific level of demand.