must firm
Regular verb: firm - firmed- firmed

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must firm
you must firm
she must firm
we must firm
you must firm
they must firm 	I must be firming
you must be firming
she must be firming
we must be firming
you must be firming
they must be firming	I must have firmed
you must have firmed
she must have firmed
we must have firmed
you must have firmed
they must have firmed	I must have been firming
you must have been firming
she must have been firming
we must have been firming
you must have been firming
they must have been firming	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I mustn't firm
you mustn't firm
she mustn't firm
we mustn't firm
you mustn't firm
they mustn't firm 	I mustn't be firming
you mustn't be firming
she mustn't be firming
we mustn't be firming
you mustn't be firming
they mustn't be firming	I mustn't have firmed
you mustn't have firmed
she mustn't have firmed
we mustn't have firmed
you mustn't have firmed
they mustn't have firmed	I mustn't have been firming
you mustn't have been firming
she mustn't have been firming
we mustn't have been firming
you mustn't have been firming
they mustn't have been firming	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I firm?
must you firm?
must she firm?
must we firm?
must you firm?
must they firm? 	must I be firming?
must you be firming?
must she be firming?
must we be firming?
must you be firming?
must they be firming? 	must I have firmed?
must you have firmed?
must she have firmed?
must we have firmed?
must you have firmed?
must they have firmed? 	must I have been firming?
must you have been firming?
must she have been firming?
must we have been firming?
must you have been firming?
must they have been firming? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
mustn't I firm?
mustn't you firm?
mustn't she firm?
mustn't we firm?
mustn't you firm?
mustn't they firm? 	mustn't I be firming?
mustn't you be firming?
mustn't she be firming?
mustn't we be firming?
mustn't you be firming?
mustn't they be firming? 	mustn't I have firmed?
mustn't you have firmed?
mustn't she have firmed?
mustn't we have firmed?
mustn't you have firmed?
mustn't they have firmed? 	mustn't I have been firming?
mustn't you have been firming?
mustn't she have been firming?
mustn't we have been firming?
mustn't you have been firming?
mustn't they have been firming?