Geostrophic Pressure Gradients

The question is this:

At wind proling radar located at 35S is used to obtain measurements of the horizontal
winds directly above the radar site. The wind velocity at 1 km is measured to be 5
ms-1 towards the North while at 3 km the wind is 5 ms-1 towards the South. A
radio-sonde launched from a nearby location measures the temperature at 1 km to be
7C. Assume the wind is purely Geostrophic and the density of air at this altitude is
1.20 kg m-3.

(b) Determine the value of the horizontal pressure gradient at 1km?

However, I thought you need two points to find the horizontal pressure gradient? How can I find it at one point?

These questions I haven't attempted as I'm stuck on b:
(c) What is the horizontal temperature gradient at 1 km? [4]
(d) Due to advection, would you expect the temperature measured at 1km to increase
or decrease with time?