A boat on the ocean is 4 mi from the nearest point on a straight shoreline;
that point is 6 mi from a restaurant on the shore (see figure). A woman plans
to row the boat straight to a point on the shore and then walk along the shore
to the restaurant.
a. If she walks at \(3 \mathrm{mi} / \mathrm{hr}\) and rows at \(2 \mathrm{mi} /
\mathrm{hr}\), at which point on the shore should she land to minimize the
total travel time?
b. If she walks at \(3 \mathrm{mi} / \mathrm{hr}\), what is the minimum speed at
which she must row so that the quickest way to the restaurant is to row
directly (with no walking)?