OKay so I found that this frame has size 72 bytes with no explanation and I can't seem to be able to figure out why .
Ethernet payload will be : ip header + arp packet
Arp packet with ip & ethrnet according to wiki has length 28 bytes.
So we have:
28 + 20 (from the header with no options) = 48 bytes (minimum payload in ethernet is 46 bytes so it's enough (?)) 48 + 14 header + 8 (sfd + preamble) = 70 bytes
What am I missing?