如圖,在矩形ABCD中,AB=12,點(diǎn)P從A點(diǎn)以每秒2cm的速度沿AB運(yùn)動(dòng),同時(shí)點(diǎn)Q從A點(diǎn)以每秒1cm的速度沿AD運(yùn)動(dòng),任何一個(gè)動(dòng)點(diǎn)到達(dá)矩形的頂點(diǎn)另一個(gè)點(diǎn)馬上停止運(yùn)動(dòng),當(dāng)點(diǎn)Q運(yùn)動(dòng)到AQ:DQ=2:3時(shí),PQ∥BD,且PQ=6.
(1)求矩形ABCD對(duì)角線(xiàn)BD的長(zhǎng)度;
(2)當(dāng)P,Q運(yùn)動(dòng)時(shí)間為t秒時(shí),求四邊形PQDB的面積y與t的函數(shù)關(guān)系,并寫(xiě)出自變量t的取值范圍.