def kdp_cover_dimensions(trim_width, trim_height, page_count, bleed, paper_thickness):
    """given trim width, page count, and paper thickness (all in inches),
    derive various KDP cover dimensions."""

    spine_width = paper_thickness * page_count
    cover_width = 2.0 * (bleed + trim_width) + spine_width
    cover_height = 2.0 * bleed + trim_height

    return cover_width, cover_height, spine_width