Lara obtained a copy of this painting of people in a train for her art collection. what art style did the painter use in this painting?

Start with what it is not.
It is not minimalism. Minimalism is characterized by simplistic drawings that look like they have been drafted by a geometry set. The lines and colors are very simple and straight. If an object you are familiar with is drawn the use of color variation is at a minimum.

It's not cubism. Cubism is characterized by it's flat 2 dimensional surface and as far as I can see lack of contrasting color. It ignores many of the techniques it took centuries to develop.

It is not Fauvism which is characterized by its powerful use of contrasting color and shape. It favors more the feeling something gives you rather than the way it actually is. 

So there is only one answer left. It is a very realistic drawing using pale light to emphasize the couple and baby(and not the young child) and a few people behind them. The yellow in the painting is very unusual. I've never seen 2 yellows used quite like that. It draws you to it, but the people themselves don't look that interesting.

Concerto grosso was composed during the classical era. (sorry if i misspelt the name)

White: titanium white.black: mars black.red: primary magenta, quinacridone red or alizarin crimson, cadmium red light.yellow: primary yellow, diarylide yellow, yellow ochre.blue: primary cyan, ultramarine blue, phthalocyanine blue.orange: pyrrole orange or cadmium orange.green: permanent green.