From the expected total calories for each bird, and find the covariance of quality and volume.
Consider the following table giving the probability that three types of birds consume two different species of caterpillars that come in two different sizes. The first has food quality (in kCal/cm3) of 1.0, and the second has food quality of 2.0. The two volumes are 0.5 and 1.5 cm3.

Volume Eaten by Bird 1 Volume Eaten by Bird 2 Volume Eaten by Bird 3 Quality 0.5 1.5 0.5 1.5 0.5 1.5 10 0.35 0.25 0.24 0.36 0.10 0.50 20 005 0.5 0.6 0.24 0.30 0.10