refractions/TIR driving me insane

[rakuenso]

A prism of refractive index 1.52 is completely immersed in water of refractive index 1.33.

A point source of light in the prism lies 60.0 cm below the

at interface between the prism

and the water. What is the diameter in centimetres of the circle at the interface through

which light emerges from the prism?

(a) 52 (b) 105 © 108 (d) 137 (e) 217

 

answer is (e)

 

but I tried everything.. with no luck

 

I calculated that the angle of incidence the light must approach the water and air must be 48.75.. past that point its all futile, the prism fubars everything up

 

sry for posting this, but it isn't a homework question, rather a review question that I just can't seem to understand