During the last 6 weeks, the actual costs of labor for Solsana Company were as follows: Week 1 $38,500 Week 2 $40,000 Week 3 $42,000 Week 4 $45,600 Week 5 $48,000 Week 6 $51,000 The standard materials cost for each week was $40,000 with an allowable deviation of 5,000. Required: Review the graphs below. a. Select the letter adjacent to the graph which represents the actual costs over time against the upper and lower limits. b. The variances that exceed the upper limit of should be investigated.