?$ A$?店:?$10 + 2 = 12($?件?$)$?
?$50\div 12 = 4($?組?$)……2($?件?$)$?
?$(4×10 + 2)×250 = 10500($?元?$)$?
?$B$?店:?$50×(250 - 50) = 10000($?元?$)$?
?$C$?店:?$50×250 = 12500($?元?$)$?
?$12500\div 1000 = 12($?組?$)……500($?元?$)$?
?$12×200 = 2400($?元?$)$?
?$12500 - 2400 = 10100($?元?$)$?
?$10000<10100<10500$?
答:在?$B$?店購買最合算。