You have recently overheard the following remarks:
(a) ‘A favourable direct labour rate variance can only be caused by staff working more efficiently than budgeted.’
(b) ‘Selling more units than budgeted, because the units were sold at less than standard price, automatically leads to a favourable sales volume variance.’
(c) ‘Using below-standard materials will tend to lead to adverse materials usage variances but cannot affect labour variances.’
(d) ‘Higher-than-budgeted sales could not possibly affect the labour rate variance.’
(e) ‘An adverse sales price variance can only arise from selling a product at less than standard price.’

Required:
Critically assess these remarks, explaining any technical terms.