A man launches his boat from point A on a bank of a straight

A man launches his boat from point A on a bank of a straight river,1 km wide,and wants to reach point B,1 km downstream on the opposite bank,as quickly as possible.He could row his boat directly across the river to point C and then run to B,or he could row directly to B,or he could row to some point D between B and C and then run to B.If he can row 6 km/h and run 8 km/h,where should he land to reach B as soon as possible?(We assume that the speed of the water is negligible compared to the speed at which the man rows.)
___________km from C