In the le receiptxlsx there is 52 observations on weekly observations on total revenue (in $1,000 units), price (in $) and advertising expenditure (in $1,000 units). Consider the statistical model tr: :51 + [3217: + B361, + [341%2 + BSatz + BGatpt + 6: This is a general quadratic function of p, and a, (it includes pf , a?) and the interaction term atpt . (a) Find expressions for the response of total receipts to price and the response of total receipts to advertising expenditure. That is, nd the partial derivatives at}; /6p, and at}; /0at . (3 marks)