Alert Rules Math Expresion

I have two expressions C and D.
C: It is a reduce expression with LAST function for input query A,
it gives me Series 1 and Series 2.
D: It is also a reduce expression with LAST function for input query A,
it gives me Series 1 and Series 2.
I want to alert if Series 1 of C < Series 1 of D
and also separate alert if Series 2 of C< Series 2 of D
How to do this?
I tried $C<$D in math expression, but it is giving combination of Series 1 and 2 in C and D, that means it is giving 4 alerts. Is there a way to reference like $C.Series 1 < $D.Series 1

This question seems to be a duplicate of Grafana OSS alerting