REGRESSION ANALYSIS & ACCOUNTIN FOR MATERIALS

Dear Mr John, Going through my study text I came across this question and solution on regression analysis. "Regression analysis was used to find the equation Y=300-4.7x, where X is time (in quarters) and Y is sales level in thousands of units. Given that X=0 represents 20X0 quarter 1 what are the quarter sales level for 20X5 quarter 4? ANSWER X=0 corresponds to 20X0 quarter 1 Therefore X = 23 corresponds to 20X5 quarter 4 Forecast sales = 300-(4.7×23) = 191.9." I understand every bit except how the "×=23" was gotten. Kindly explain. 2) A manufacturing company uses 25000 components at an even rate during a year. Each order placed with the supplier of the component is for 2000 components which is the reorder quantity. The company holds a buffer inventory of 500 component site. The annual cost of holding one component in inventory is $2. What is the total annual cost of holding inventory of the component? Answer [Buffer inventory + (EOQ/2)] x annual cost Ie $3000 My question then is, can I conveniently say the total annual cost = average inventory x annual holding cost cost per component? Thank you