Anna's Antiques expects to get two bidders for the unique china teacup it sells. Each of the bidders can either have a high-value of $100 or a low-value of $70 with equal probability. If Anna receives $100 from the auction she can infer that

a. Both the bidders were high value bidders
b. Both the bidders were low value bidders
c. One of the bidders was high value, while the other was low value
d. All of the above

a