（1）No.PZ2020012001000017 (问答题)
来源: 品职出题
Suppose that on a particular day there are 3,000 trades in a futures contract. Of the buyers in those 3,000 trades, 1,800 were closing out positions and 1,200 were taking new positions. Of the sellers in those 3,000 trades, 1,400 were closing out positions and 1,600 were taking new positions. What is the change in open interest during the day? Does it increase or decrease?
这题课后没给出open interest的答案，此外，这题解析的计算过程感觉不详细，希望给一个逻辑性较好的解题方法和思路
（2）No.PZ2020012001000015 (问答题)
来源: 原版书
If the options (concerning delivery times and what can be delivered) available to the party with a short position are increased, do you think the futures price increases or decreases? [Hint: An option always has a positive value to the holder of the option.]
解析
The more options that the party with a short position has the more attractive the contract is to that party. They are therefore prepared to agree to a lower delivery price. Options available to the party with a short position therefore tend to lower the delivery price.
首先，我感觉解析没有回答题目的问题，future price到底是increase还是decrease，其次，这个解析没有看懂，为什么会lower delivery price，最后，我理解，如果卖方的option更多，那么期货的价格应该会更低，但是和delivery price有什么关系呢？
