scRNAseq, how many genes are unique to each type vs combinatorially expressed?

Question

[I-Hao]

Hello, I'm working on analyzing the single-cell RNAseq data analysis and I got a question for a quantitative way to quantify the transcriptional heterogeneity across the neuron subtype, more specifically, I'm asked to make a quantitative measurement of how many genes are unique to each type vs combinatorially expressed?

I'm having a hard time coming up with a good analysis/plot for answering this question, any discussion/suggestions are welcome, thanks in advance!