Bill, a builder, wants to submit a bid on a city sewer project. He computes the cost, but mistakenly omits the cost of one item. Accordingly, he submits a bid of $$430,000$ to the city. The next highest bid is $$675,000,$ and the rest of the bids are even higher. The city is happy to have such a low bid, so it accepts Bill's bid and awards him the contract for the job, even though the city engineer is of the opinion the job cannot be done for less than $$650,000.$

Question $9$Select one:

a$.$

Bill must perform for the agreed upon price, because he has made a unilateral mistake.

b$.$

The city was aware of Bill's mistake. When it accepted the bid, with knowledge of Bill's mistake, the city sought to take an unconscionable advantage of Bill's error.

c$.$

This case is an example of a palpable unilateral mistake.

d$.$

Two of the above, $($b$)$ and $($c$).$