Bs 1377

I have a task that says: make a file (called BinaryFiles) which contains 4 bytes of data NULL, 6 bytes of random data, 8 bytes 1, 5 and 10 bytes 12 bytes 9.
For the first two, can I use dd if = / dev / null bs of BinaryFiles = = 8 = 4 and count dd if = / dev / urandom of = bs = 8 count = BinaryFiles 6 seek = 4, but how can I do the rest???

I like to use a hex editor, and enter the data manually.