A regression analysis was performed to determine the relationship between the costs of a product (y), the time to make the product (x1 ), the number of different materials used (x2), and the amount spent on marketing the product (x3). The estimated regression equation is ŷ = 83- 2x1+ 6x2 + 1.1x3. What is the estimated cost if the time to make the product is 5 hours, the number of different materials used is 4, and the amount spent on marketing is $100?

a. 83
b. 213
c. 185.4
d. 205.

The management of a supermarket wants to adopt a new promotional policy of giving a free gift to every customer who spends more than a certain amount per visit at this supermarket. the expectation of the management is that after this promotional policy is advertised, the expenditures for all customers at this supermarket will be normally distributed with a mean of $95 and a standard deviation of $20. if the management wants to give free gifts to at most 10% of the customers, what should the amount be above which a customer would receive a free gift?