I could summate you could summate she could summate we could summate you could summate they could summate
V-ing form
I could be summating you could be summating she could be summating we could be summating you could be summating they could be summating
Perfect
I could have summated you could have summated she could have summated we could have summated you could have summated they could have summated
V-ing perfect
I could have been summating you could have been summating she could have been summating we could have been summating you could have been summating they could have been summating
Negation
Simple form
I could not summate you could not summate she could not summate we could not summate you could not summate they could not summate
V-ing form
I could not be summating you could not be summating she could not be summating we could not be summating you could not be summating they could not be summating
Perfect
I could not have summated you could not have summated she could not have summated we could not have summated you could not have summated they could not have summated
V-ing perfect
I could not have been summating you could not have been summating she could not have been summating we could not have been summating you could not have been summating they could not have been summating
Interrogative form
Simple form
could I summate? could you summate? could she summate? could we summate? could you summate? could they summate?
V-ing form
could I be summating? could you be summating? could she be summating? could we be summating? could you be summating? could they be summating?
Perfect
could I have summated? could you have summated? could she have summated? could we have summated? could you have summated? could they have summated?
V-ing perfect
could I have been summating? could you have been summating? could she have been summating? could we have been summating? could you have been summating? could they have been summating?
Interro-negative form
Simple form
could I not summate? could you not summate? could she not summate? could we not summate? could you not summate? could they not summate?
V-ing form
could I not be summating? could you not be summating? could she not be summating? could we not be summating? could you not be summating? could they not be summating?
Perfect
could I not have summated? could you not have summated? could she not have summated? could we not have summated? could you not have summated? could they not have summated?
V-ing perfect
could I not have been summating? could you not have been summating? could she not have been summating? could we not have been summating? could you not have been summating? could they not have been summating?