The duration of the call is 3.5 hours.
1	The	the	DET	DT	Definite=Def|PronType=Art	2	det	2:det	_
2	duration	duration	NOUN	NN	Number=Sing	8	nsubj	8:nsubj	_
3	of	of	ADP	IN	_	5	case	5:case	_
4	the	the	DET	DT	Definite=Def|PronType=Art	5	det	5:det	_
5	call	call	NOUN	NN	Number=Sing	2	nmod	2:nmod:of	_
6	is	be	AUX	VBZ	Mood=Ind|Number=Sing|Person=3|Tense=Pres|VerbForm=Fin	8	cop	8:cop	_
7	3.5	3.5	NUM	CD	NumForm=Digit|NumType=Card	8	nummod	8:nummod	_
8	hours	hour	NOUN	NNS	Number=Plur	0	root	0:root	SpaceAfter=No
9	.	.	PUNCT	.	_	8	punct	8:punct	_
