Help with dimension on steel beam in garage

[mini_cooper_s]

Anyone who can help with the dimension of a steel beam in a garage!?

I'm going to replace the roof from asbestos cement to roof tiles and thought to also replace the beam running along one long side (where the doors are), but I have no idea which beam I should use.

The total length will be 7m, but I was thinking of setting 3 posts so the longest self-supporting section will be about 4m.

The roof will be roof tiles with board as the underlayer, about 28-degree slope, and it's about 3.7m from the gutter to the ridge.

Snow zone: 1.5

Is there any structural engineer who can calculate which size I should use in, for example, HEA?

(What should I use for posts, is 90x90 structural steel okay?)

Grateful for any help I can get!
/Jonas

 

[mini_cooper_s]

I have received a proposal from a company that sells used beams (he didn't do any calculations but relied on experience):
7m Beam: HEA 160 (160mm H beam)
Posts 3x 2.6m: 90x90x3.6
Price: 6:-/kg i.e. 1276:- for the beam and 521:- for the posts totaling approx 1800:-

To my ears, both the dimensions and price sound okay, what do you think?