求教一道pp

To celebrate a colleague's retirement, the T coworkers in an office agreed to share equally the cost of a catered lunch. If the lunch costs a total of X dollars and S of the coworkers fail to pay their share, which of the following represents the additional amount, in dollars, that each of the remaining coworkers would have to contri bute so that the cost of the lunch is completely paid?

A. X/T    B. X/(T-S)   C. SX/(T-S)   D. SX/T(T-S)  E. X(T-S)/T

选d

x/(t-d)  -   c/t 

多谢~做题的时候没注意要求additional amount。。。