Calvin is performing the following auditing procedures related to revenues: (i) obtaining production records of physical quantities sold and calculating an estimate of total sales dollars based on average selling prices; (ii) comparing revenue dollars and physical quantities with prior-year data and industry economic statistics. Which types of evidence-gathering procedures is Calvin using?

a. (i) Observation; (ii) confirmation

b. (i) Recalculation; (ii) analysis

c. (i) Recalculation; (ii) inspection (vouching)

d. (i) Analysis; (ii) analysis