How are these types of time dilation related? How are these two phenomena related (if at all):
1. Gravitation slowing down time
2. High speed slowing down time
 A: In relativity there's no objective frame-independent way to compare the rate two clocks at different locations are ticking--different coordinate systems can give different answers (ultimately this is due to the relativity of simultaneity). There is also no frame-independent notion of speed, so you can't say in any objective sense that clocks moving at high speed slow down, though you can say that relative to any given inertial frame, clocks with greater speeds in that frame tick slower in that frame. The most objective way to talk about differences in time elapsed is to compare clocks at the same location, move them apart, and then bring them back together to compare at a common location. In this case, a coordinate-independent consequence of gravitational time dilation could be seen if one clock moved closer to a source of gravity like a planet, spent some time at a shorter distance, and then moved back out to reunite with a clock that remained farther away. And a coordinate-independent consequence of velocity-based time dilation could be seen if one clock moved inertially between the meetings, while the other accelerated to turn around once they had moved apart for some time (see the twin paradox).
Ultimately, the difference in time elapsed in both scenarios can be derived from the rule that a time-like geodesic path between events in spacetime (the closest equivalent to a 'straight line' path between the events) is the one that locally maximizes the proper time. But if you aren't familiar with terms like "geodesic" and the notion of evaluating "proper time" along a path using the "metric" of a given spacetime, this would require a fair amount of explanation. You could try a conceptual introduction like General Relativity from A to B to learn about the basic ideas involved here.
A: I believe the answer you are looking for is in the link below.
If you take how many Schwarzschild Radii you are from the center of a mass (or how deep you are in a gravitational field) it is equal to how many times faster light is going squared.
x=y^2
so if you are 4 (x) Schwarzschild radii from the center of a mass then to calculate the equivalent time dilation due to velocity you would solve for y which would be two in this case showing that the speed of light is going two times faster than the observed object.
let me know if this helps.
https://physics.stackexchange.com/questions/150542/time-dilation-geometry
