Geomerty doesn't quiet cut this for me

Car A in traveling on a straight road on a bearing of 300 degrees, at a constant speed on 80 km/h. at 10 am it is 15 Km due east of a second car B which is also traveling at a constant speed. assuming that car B can travel in any direction

a) find the minimum speed of B if it is to intercept A.

Thanks Bobak