Rudolf takes one hour to set $30$ questions, so he takes $2$
minutes to set each question. We're told each person takes half as
long as the previous person to set questions, so we can work out
how long each person takes to set one question, then multiply by
the number of questions to give the time each setter spent on all
their questions:
Setter 
Time taken to
set each question (minutes)

Number of
questions set 
Total time spent
setting questions (minutes) 
John 
$8$ 
$25$ 
$200$ 
Peter 
$4$ 
$26$ 
$104$ 
Rudolf 
$2$ 
$30$ 
$60$ 
Susie 
$1$ 
$39$ 
$39$ 
Tony 
$\frac{1}{2}$ 
$55$ 
$27 \frac{1}{2}$ 
So in total the setters spent: $$ 200+104+69+39+27 \frac{1}{2}
\;\text{minutes}= 430 \frac{1}{2} \text{minutes} $$ or $$7 \;
\text{hours } \; 10 \; \text{minutes }\; 30 \; \text{seconds }$$
setting questions.
This problem is taken from the UKMT Mathematical Challenges.