一 How much are the two packets of ____ (battery)?
一 Ten yuan, please.
①2.5×7.1×4②16.12×99+16.12③5.2×0.9+0.9×4.8
如图,正方形ABCD的边长为4,点E在边BC上且CE=1,长为2的线段MN在AC上运动,当四边形BMNE的周长最小时,则tan∠MBC的值是____.