Variance Analysis

The finance director of Paint Mixers Ltd has produced the table below showing the variance
results for the first three months of the year:
January February March
Material price variance $3,000 A $2,000 A $1,000 A
Material mix variance $2,000 A $750 A $100 F
Material yield variance $4,000 A $2,000 A $50F
Which of the following interpretations of the variances analysis exercise above is NOT
correct?
A The purchasing manager should be able to threaten to switch suppliers to get better
deals and address the adverse material price variance
B The materials mix variance is entirely under the control of the production manager
C The favourable yield variance in March could be the result of operational efficiency
D The responsibility for the initial poor performance must be borne by both the
purchasing manager and the production manager

The answer is D.. The production manager controls both the mix and the production process and must
alone bear responsibility for this initial poor performance.

But the above question has material price variance also which is adverse.. isn’t it the responsibility of the purchasing manager also? so does the purchasing manager not responsible for the poor performance?? Why only production manager?