Movie companies need to predict the gross receipts of individual movies after a movie has debuted. The accompanying results are the first weekend gross, the national gross, and the worldwide gross (in millions of dollars) of six movies. Complete parts (a) through (d) below. Click the icon to view the gross receipts of the six movies. a. Compute the covariance between first weekend gross and national gross, first weekend gross and worldwide gross, and national gross and worldwide gross. Find the covariance between first weekend gross and national gross. (Round to four decimal places as needed.)