 Okay, so this one says, rank the following in order of increasing reactivity relative to substrate effects in an SN1 reaction, okay? So we're looking at SN1 and substrate means starting material like the alkyl halides that are being shown here, okay? So in an SN1 reaction, do you remember SN1 reactions? What reacts fastest in an SN1 reaction when we're talking about the alkyl halide? Tertiary. Okay, tertiary is the fastest. So it says in order of increasing reactivity, so the highest is 4, okay? So this one, as everybody sees, is the tertiary, right? So we're going to put a 4 there, okay? And then secondary is the next fastest, right? Is everybody on board with what we're doing here? Okay, secondary is the next fastest. You see the secondary there? Then the primary is next. Probably won't react to any appreciable extent if you tried to do an SN1 reaction. And then the one that would react the least is definitely methyl bromide there, okay? Why? Because it's very difficult to make a methyl carbocation. It's very, very much easier to make a tertiary carbocation, okay? And remember, that's the rate-determining step of an SN1 reaction. Any questions on this one?