Does the Fireball from Kiss of Mephistopheles cast at the same level as other spells?

Question

Unearthed Arcana: Revised Class Options shows the Eldritch Invocation named Kiss of Mephistopheles:

Prerequisite: 5th level, eldritch blast cantrip

When you hit a creature with your eldritch blast, you can cast fireball as a bonus action using a warlock spell slot. The spell must be centered on the creature you hit with eldritch blast.

My warlock is level 12, meaning all her spells slots are of 5th level.

QUESTION

By RAW, would the triggered fireball in this case also be cast at 5th level?

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Related:

• Does the UA warlock invocation Kiss of Mephistopheles require you to know the Fireball spell?

Answer 1

Yes, because you use one of your spell slots to cast fireball.

As mentioned, the warlock table shows that at class level 12 your spell slots are of 5th level. The invocation states you can cast fireball using one of your spell slots:

When you hit a creature with your eldritch blast, you can cast fireball as a bonus action using a warlock spell slot.

Following the text that comes with the table (emphasis mine):

Spell Slots

The Warlock table shows how many spell slots you have to cast your warlock spells of 1st through 5th level. The table also shows what the level of those slots is; all of your spell slots are the same level.

If you cast fireball using one of those spell slots, the fireball would be cast at 5th level too.