Help with latent and sensible heat gains

http://img.photobucket.com/albums/v518/themastertaylor/ques001.jpg

I've been set an assignment and have an issue with parts a and b at the top of the page. I've completed the question as i interpret it and so has a friend, however we've got completely different answers and can't decide who's right.

Occupants 140 x 4= 560
Bulbs 60 x 4= 240
A-V Equipment 100 x 1= 100
Appliances 500 x 1= 500
Total Heat Gain/ watts = 1400

Heat gain /Floor area = 1400/150

= 9.33 Watts/M2

Whereas my friend has something along these lines:

he's broke it down to sensible and latent gains, as such he's not combined the gains from the people as i have above but has the same result via a longer method. where things differ is that he has allowed a latent and sensible gain from the light bulbs av equipment etc whereas i've only used them once.

In essence i'm trying to establish if the lights give a gain of 60W in both latent and sensible heat gain or should they just be calculated once as I have done?

He's also used the same approach in part b with the photocopier for example.