During the last 6 weeks, the actual costs of materials for Brennen Company were as follows:

Week 1 $57,600 Week 4 $68,400 Week 2 $60,000 Week 5 $69,000 Week 3 $63,000 Week 6 $69,500

The standard materials cost for each week was $60,000 with an allowable deviation of 6,000.

Required:

1)Plot the actual costs over time against the upper and lower limits.

2)Comment on whether or not there is a need to investigate any of the variances.