Linda wants to do two coats, so the total area she will be painting is 2 coats * 600 sq. ft./coat = <<2*600=1200>>1200 sq. ft.
A gallon of paint will cover 400 sq. ft., so Linda will need 1200 sq. ft. / 400 sq. ft. per can = <<1200/400=3>>3 cans of paint
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