The formula for dynamic hydoplaning.....
= 9√P for a rotating tyre
= 7.7√P for a non rotating tyre
P is the tyre pressure in PSI.....the questions may give you tyre pressure in BARS, to convert....
BARS x 14.5 = PSI

Q. The questions do not seem to state whether the tyre is rotating or not. What should I assume?

A. The questions have only recently started to distinguish......but with no other info, we would assume rotating tyre.....but let us know if they don't specify!!