probability for filling fuel

Question

I'm trying to solve below probability question ;

fuel station has $5$ filling points of which $3$ are use to fill petrol and remaining $2$ are use to fill diesel for different kind of vehicles.It was noticed that an average $3$ minutes to fill fuel to any vehicle (diesel/petrol).number of petrol vehicles to enter the fuel station within an hour estimated is $24$ and the diesel vehicle estimated 36 within an hour.

want to find below probabilities :

1. all petrol filling points are idle
2. all diesel filling points are busy
3. all petrol filling points are busy
4. all filling points are busy

Answer 1

It was noticed that an average 3 minutes are required to fill fuel to any vehicle. As there are 3 petrol filling points, they can fill fuel petrol to petrol vehicles at the most 60 per hour. As number of petrol vehicles entering into fuel station are 24, The probability that all the 3 petrol points will remain idle is $\binom{3}{3}(\frac{24}{60})^0(\frac{36}{60})^3=0.216$

Likewise, You calculate the answers to other questions.

Answers to the other questions are as follows:

2)$\binom{2}{2}(\frac{36}{40})^2(\frac{4}{40})^0=0.81$

3)$\binom{3}{3}(\frac{24}{60})^3(\frac{36}{40})^0=0.064$

4)$\binom{5}{5}(\frac{60}{100})^5(\frac{40}{100})^0=0.0776.$