Grafana + Prometheus: Query to display the highest of three values in singlestat panel


I am trying to find a way to write a query in grafana which will display only the highest of three values (coming from kube.state.metrics / prometheus) in a singlestat panel.

I have tried using max(), but this only returns the highest value in a timeline of a single metric.

I am looking to get the following output:
Variables: a = 10, b = 15 , c = 4
Query: maxValue(a, b, c)
Result: 15

Is this possible in Grafana / PromQL?

Thanks for your help