John's Weed-B-Gone yard service sprays lawns to rid them of weeds. John mixes the two chemicals, Weed-X and Pest-O, in proportions depending on the climate and the particular weed problems of the season. A standard mix calls for a gallon of the mixture to combine equal parts of Weed-X and Pest-O. Weed-X has a standard cost of $10 per gallon and Pesto-O has a standard cost of $25 per gallon. Each gallon can treat 100 square yards of lawn. John expects to treat 540,000 square yards of lawn.

For the past season, John treated 648,000 square yards. He used 3,600 gallons of Weed-X and 3,000 gallons of Pest-O. He paid a total of $35,280 for the Weed-X and $72,000 for the Pest-O.

a. Compute the materials price and efficiency variances for the season.

b. Compute the materials mix and yield variances for the season.