问题如下：
Describe the different calculations that must be carried out in a P&L decomposition.
选项：
解释：
We first calculate the carry roll-down. This has two components: the cash-carry (i.e., the coupon payment) and the change in price. In calculating the carry roll-down, we assume that the spread remains unchanged. We then calculate the value of the bond for the actual change in the term structure assuming again that the spread remains unchanged. Finally, we calculate the effect on the bond price of the spread change.
请问P&L是什么的首字母？
