How does Haste interact with Boots of Striding and Springing?

Question

So I am currently playing a vine leshy ninja in Pathfinder 1e. I am taking the Acceleration of Form ninja trick and Boots of Striding and Springing. Important information that you need to know before I ask the question:

• The race’s speed is listed as 20 feet.
• The boots give a +10 bonus to base speed. This is an enhancement bonus.
• Haste increases all forms of movement by 30 feet to a maximum of twice the subject’s normal speed using that form of movement. This is an enhancement bonus.

So my question at hand is: how do these interact?

So far me and my gm have come up with three possible answers:

1. Haste doubles race move speed, replaces boots as they are both enhancement (Total 40 feet).
2. Haste doubles your move speed, replaces boots as both are enhancement (Total 50 feet).
3. Haste doubles your move speed - but the enhancement bonus to base speed is different than bonus to total speed and as a result they stack (total 60 feet).

What is the proper interaction between these effects?

Answer 1

It's #1

The creature's land speed can only benefit from one enhancement bonus. To determine the creature's speed while it's wearing the boots of striding and springing and affected by a haste spell…

1. determine the creature's speed using only the effect of the boots of speed; then…
2. determine the creature's speed using only the haste spell.

After that, the creature uses the higher of those two speeds. This is because both the boots and the haste spell offer an enhancement bonus, and the two don't combine. (For more on stacking see here.)

Even though the creature is getting an enhancement bonus to all of its modes of movement from the haste spell, that enhancement bonus from the haste spell applies to the creature's land speed in addition to applying to other speeds. The enhancement bonus from the haste spell is not an enhancement bonus to a new value named All of the hasted creature’s modes of movement.