Roulette It takes a math expert to know double ball roulette odds and payout

There is a double ball roulette owned by evolution gaming software, online gambling
in a single-zero wheel

A corner bet pays 3,5+1=4,5
You bet 1 and you get 4,5 if one of the balls hit one of the 4 numbers
In case both balls hit any of the 4 numbers you get 9 units.
What is the chance to hit 1 or the 2 balls?

For the 1st ball is 4/37, the 2nd has the same chance, when you hit both balls at the corner you get 9 units. How often does it happen?
To to get 9 units you must hit every spin for 2 trials, 4,5+4,5
So, you sometimes save 0,50, it shorten the HE
Do any know the exact payout and odds?