A. The favorable materials price variance means that the material was purchased for a lower price than planned. This could happen due to a quantity discount, lower quality materials, or some other reason. The unfavorable materials usage variance means that the production process used more material than had been planned. This could happen due to a lower skill level of workers, poor material quality or some other reason. However, these two variances together are most likely caused by the same reason. This reason could be the purchase of lower than standard quality materials.

B. The purchase and use of higher than standard quality materials would most likely result in an unfavorable materials price variance and either not significantly affect the material usage variance or would lead to favorable material efficiency variance.

C. Product mix production changes would not cause the materials price variance.

D. Machine efficiency problems would not cause the materials price variance.