Brenda drives an 18 wheeler. she plans to buy her own truck. Her research indicates that the expected running costs, C, in dollars, per 100 km, are given by C(v)=0.9 +0.0016v square, where v is the speed, in kilometers per hour. Brenda's first trip will be 1500 km, round trip. she plans to pay herself $30/h. determine the speed that will minimize Brend's cost for the trip