A Local Tire Dealer Wants to Predict the Number of Tires

Short Answer

A local tire dealer wants to predict the number of tires sold each month. He believes that the number of tires sold is a linear function of the amount of money invested in advertising. He randomly selects 6 months of data consisting of tire sales (in thousands of tires) and advertising expenditures (in thousands of dollars). Based on the data set with 6 observations, the simple linear regression model yielded the following results.
∑X = 24
∑X² = 124
∑Y = 42
∑Y² = 338
∑XY = 196
Find the estimated slope.