Last year, Sandra bought 6 pairs of shoes when her income was $40,000. This year, her income is $35,000, and she purchased 7 pairs of shoes. What can we determine about Sheila?

A. Sheila's income is higher than Sandra's.
B. Sheila's income is lower than Sandra's.
C. Sheila's income is the same as Sandra's.
D. We cannot determine anything about Sheila's income.