Closing prices of two stocks are recorded for 50 trading days. The sample standard deviation of stock X is 4.561 and the sample standard deviation of stock Y is 8.831. The sample covariance is $36.040.

Plastic and steel are substitutes in the production of body panels for certain automobiles. if the price of plastic increases, with other things remaining the same, we would expect: a) the demand curve for plastic to shift to the left. b) the price of steel to fall. c) the demand curve for steel to shift to the left d) nothing to happen to steel because it is only a substitute for plastic. e) the demand curve for steel to shift to the right