mot khoi go hinh hop chu nhat co kich thuoc dai:40m r:30m c:20m duoc son 4 mat nhung khong ro mat nao nay nguoi ta dem cat thanh cac khoi go hnh hop chu nhat co kich thich dai;4cm rong ;3cm cao ;2cm
a) cat duoc duoc bao nhieu khoi nho
b) co bao nhieu khoi duoc son 3 mat 2mat 1mat va khong son mat nao