Nine
The wave lengths are red herrings. (That means you don't need them). Don't worry, it fooled me too.
You have to calculate the sine of the angle twice and then take the difference.
n = sin(i)/sin(r)
sin(r) = sin(i) / n
sin(r) = sin(42.8) / 2.46
sin(r) = 0.2762
r = sin-1(0.2762)
r = 16.03 degrees. The angle of refraction is 16.03 degrees for n = 2.46
=================
sin(r) = sin(i)/n
sin(r) = sin(42.8)/2.41
sin(r) = 0.2819
r = sin-1(28.19)
r = 16.375
=======
The difference = 16.375 - 16.03 = 0.345 degrees or 0.35
Ten
It's an awfully strange way to define what's going on but as near as I can tell the refracted ray is tangent to the surface. No guarantees issued on this question, but nothing else makes sense.