Madden's Camera Shop has prepared the following flexible budget for September and is in the process of interpreting the variances. F denotes a favorable variance and U denotes an unfavorable variance. Flexible Variances Budget Price Efficiency Material A $20,000 $1,100U $2,000F Material B Material C 38,000 49,000 300F 1,300U 200U 2,300F The explanation that lower-quality materials were purchased is most likely for OA. Material A B. Material B C. Material C D. both Material A and C