若整式M，N满足式子M+N=x2﹣3，其中M=3x﹣3，求N．
解：N=（M+N）﹣M
=（x2﹣3）﹣（3x﹣3）
=x2﹣3﹣3x+3
=x2﹣3x．
考察在一段固定长度的时间内到达某场所的交通数量的波动性可采用（）。
In an effort to plan out expenses, the Roberts family is representing its annual budget as a circle graph. Each sector of the graph is proportional to the amount of the budget it represents. If "clothes and shoes" takes up 54° of the chart, how much of the Roberts’s $20,000 annual budget is dedicated to clothes and shoes ？（）
A. $1,500
B. $3,000
C. $4,500
D. $5,000
E. $5,400
