单选题
If the cost of a long—distance phone call is c cents for the first minute and 
cents for each additional minute，what is the cost，in cents．of a 10-minute call of this type?
cents for each additional minute，what is the cost，in cents．of a 10-minute call of this type?
【正确答案】
D
【答案解析】若长途电话费为第一分钟收c美分，以后每增加一分钟，加收[*]美分，那么按这种计费方式打10分钟的电话需付多少钱(以美分为单位)?
由题意可得：
[*]
由题意可得：
[*]