Stimulus size/Visual distance calculation for fMRI imaging?

I am using fMRI imaging in my study (Flanker Task) where I am lost at how to calculate the Stimulus size. I have the visual angle information for my stimulus but I am unable to convert that information into pixel size. In the fMRI setting, the projector screen is placed at the back of the participant's head behind the scanner and the images are projected to an angular mirror on the head coil which then gets reflected in the participant's eyes.

For conversion of visual angle to pixel size, we generally need the visual distance which in this case cant be just the distance between the screen to the eye. I am not sure how to take into account the angular arrangement of the head coil mirror into this calculation or if we need to account for mirror dimension as well.

Following is the information we have,

 

Given Stimulus Visual angle= 3.28 on x-axis, 0.41 on y-axis

Screen to mirror distance = 160 cm

The mirror is at a 45-degree angle to the head

Mirror to eye distance = 14 cm

Screen dimention: 1920x1080(resolution)

87.5 cm (Width), 48.3 (Height)

Mirror dimentions = 15.5 cm (Width), 12 cm (Height)

 

Question: What would be the pixel size or dimensions(height/width) for the Stimulus?

 

Any help would be greatly appreciated. Thank you.