It is known that the period of the earth's revolution around the sun is t, the distance between the earth and the sun is r, and the gravitational constant is g?

Let the mass of the sun be m, then GM / R ^ 2 = RW ^ 2 = R (2 π / T) ^ 2 is m = 4R ^ 3 π ^ 2 / (GT ^ 2)

Senior to help solve two high school physics problems, very urgent. Online and so on
The first way: a small boat crosses to the opposite bank in a 100m wide river. The known water velocity is 3m / s, and the speed of the small boat in still water is 5m / S. in order to make the crossing distance shortest, how much angle should the bow keep with the river bank? What are the crossing time and displacement?
The second way: throw a small ball horizontally from 1.8m high. The angle between the ball's speed and the horizontal ground is 45 ° when it lands. Calculate the initial speed and horizontal displacement when it is thrown
The second way will do, just ask for the detailed answer of the first way!

Linear past displacement S = 100m
cos a=3/5
Angle a = 57
Closing speed v = 4m / S
t=25s