[填空题]
A boat, whose speed in still water ij+8)kzy ah( xps 1.75 m/s, must ai ,c)x4witot2km upstream at an angle oftik2,o tc 4w)x $26.3^{\circ}$ (with respect to a line perpendicular to the shore) in order to travel directly across the stream. (a) Determine the speed of the current. $m/s$ (b) Determine the resultant speed of the boat with respect to the shore $m/s$
