6. In the regression model Y=$100,000+$10X, Y is total Repairs \& Maintenance (R&M) cost and X is machine hours. The above equation implies that an a. increase of 1 machine hour is associated with an increase of $10,000 in total R\&M cost. b. increase of 1 machine hour is associated with an increase of $10 in total R\&M cost. c. increase of 10 machine hours is associated with an increase of $110,000 in total R\&M cost. d. increase of 10 machine hours is associated with an increase of $10,000 in total R\&M cost