The correct answer is (a) v = 1.85 X 10^8m/s

For explanation: Using Snell’s law, refractive index of glass slab = sin i/sin r

Also, the refractive index of glass slab = c/v

Therefore, c/v = sin i/sin r

v = c X sin r/sin i

v = 3 X 10^8X sin 30^o/ sin 54^o

v = 1.85 X 10^8m/s.