Am looking to light an open shop area that has 9' drywall ceilings painted white. Dimensions are 30'x40'. Would like some help(possibly a formula) to determine amount of light needed. Fixtures will be 8' florescent open strips total of 4 48" tubes per fixture(referred to as tandems). Lamps are 32W 4100K. Owner wants it to be "very bright", I realize that this request means something different to everyone, but a starting point would be helpful. Thanks.