Question: each pixel in a laptop display subtends 005 degrees if...

Each pixel in a laptop display subtends 0.05 degrees. If every other column of pixels is lit up to form a grating, at a viewing distance of 450mm the grating will have a spatial frequency of:

a) 0.05 cpd

b) 0.13 cpd

c) 10 cpd

d) 20 cpd