The formula is
Net price= list price-trade discount
List price 475
Trade discount=list price×trade discount rate
Trade discount=475×0.15=71.25
Net price=475−71.25=403.75
But your options are in different way
To find The net price after the trade discount is 85% (100%-15%)
So the correct setup to find net price is C. Net Price = $475 * 85%
Net price=475×0.85=403.75