程序如下，想请教的是为什么在street后加冒号修饰符，在price后加&修饰符。
data work.condo_ranch1;
infile cards dsd ;
input style $ sqfeet bedrooms baths street:$16. price & dollar10.;
cards;
ranch,1250,2,1,sheppard Avenue,"$64,000"
split,1190,1,1,rand street,"$65,850"
condo,1400,2,1.5,market street,"$80,050"
ranch,1500,3,3,Kemble Avenue,"$86,650"
split,1305,3,1.5,graham Avenue,"$73,650"
;
run;